Add a formula to the focused cell of XLSX worksheet

public void AddFormulaToXlsxCell(Vintasoft.Imaging.Office.Spreadsheet.UI.SpreadsheetEditorControl editorControl)
{
    // get visual editor for spreadsheet document
    Vintasoft.Imaging.Office.Spreadsheet.UI.SpreadsheetVisualEditor spreadsheetVisualEditor = editorControl.VisualEditor;

    string formula = "ABS(A1)+SUM(B2,B3)";

    // add formula to the focused cell
    spreadsheetVisualEditor.InsertFormulaInFocusedCell(formula);
    // result formula value: "=ABS(A1)+SUM(B2,B3)"
}

Public Sub AddFormulaToXlsxCell(editorControl As Vintasoft.Imaging.Office.Spreadsheet.UI.SpreadsheetEditorControl)
    ' get visual editor for spreadsheet document
    Dim spreadsheetVisualEditor As Vintasoft.Imaging.Office.Spreadsheet.UI.SpreadsheetVisualEditor = editorControl.VisualEditor

    Dim formula As String = "ABS(A1)+SUM(B2,B3)"

    ' add formula to the focused cell
    spreadsheetVisualEditor.InsertFormulaInFocusedCell(formula)
    ' result formula value: "=ABS(A1)+SUM(B2,B3)"
End Sub

Change formula of focused cell programmatically

public void ChangeValueOfXlsxCell(Vintasoft.Imaging.Office.Spreadsheet.UI.SpreadsheetEditorControl editorControl)
{
    // get visual editor for spreadsheet document
    Vintasoft.Imaging.Office.Spreadsheet.UI.SpreadsheetVisualEditor spreadsheetVisualEditor = editorControl.VisualEditor;

    // get value or formula of focused cell
    string cellValue = spreadsheetVisualEditor.FocusedCellValue;

    // set value or formula of focused cell
    spreadsheetVisualEditor.FocusedCellValue = "0";
}

Public Sub ChangeValueOfXlsxCell(editorControl As Vintasoft.Imaging.Office.Spreadsheet.UI.SpreadsheetEditorControl)
    ' get visual editor for spreadsheet document
    Dim spreadsheetVisualEditor As Vintasoft.Imaging.Office.Spreadsheet.UI.SpreadsheetVisualEditor = editorControl.VisualEditor

    ' get value or formula of focused cell
    Dim cellValue As String = spreadsheetVisualEditor.FocusedCellValue

    ' set value or formula of focused cell
    spreadsheetVisualEditor.FocusedCellValue = "0"
End Sub

Edit the formula of the focused cell using mouse and keyboard

• Start editing the cell value
• Enter '=' symbol into the cell value
• Click on the cell that should be referenced and the cell address will be added to the formula

• Start editing the cell value
• Enter '=' symbol into the cell value
• Enter the formula name (for example "SUM") in the cell value
• Enter symbol '(' into the cell value
• Press Ctrl key and click on the cells, which values should be used in the formula, cells addresses will be added to the formula

• Start editing the cell value
• Used cells will be highlighted using blue regions
• Used cell will be highlighted using red region if the cell address is under text caret
• Used cells will be highlighted using red region if the region of cell addresses is under text caret

Delete the formula of focused cell of XLSX worksheet

• Click on the cell, which formula should be deleted.
• Press "Del" key.

public void ClearXlsxCell(Vintasoft.Imaging.Office.Spreadsheet.UI.SpreadsheetEditorControl editorControl)
{
    // get visual editor for spreadsheet document
    Vintasoft.Imaging.Office.Spreadsheet.UI.SpreadsheetVisualEditor spreadsheetVisualEditor = editorControl.VisualEditor;

    // clear contents (value and formula) of selected cells
    spreadsheetVisualEditor.ClearCellsContents();
}

Public Sub ClearXlsxCell(editorControl As Vintasoft.Imaging.Office.Spreadsheet.UI.SpreadsheetEditorControl)
    ' get visual editor for spreadsheet document
    Dim spreadsheetVisualEditor As Vintasoft.Imaging.Office.Spreadsheet.UI.SpreadsheetVisualEditor = editorControl.VisualEditor

    ' clear contents (value and formula) of selected cells
    spreadsheetVisualEditor.ClearCellsContents()
End Sub

List of supported formulas

• DATE - Computes the serial date-time for the given date.
• DATEDIF - Calculates the number of days, months, or years between two dates.
• DATEVALUE - Computes the serial date-time of the date represented by the string date-time-string, taking into account the current date system.
• DAY - Computes the numeric day of the month in the Gregorian calendar for the date and/or time having the given date-value, taking into account the current date system.
• DAYS360 - Computes the signed number of days between two dates based on a 360-day year (twelve 30-day months).
• EDATE - Computes the serial date-time of the date that is month-offset months from the date specified by the date date-string, taking into account the current date system.
• EOMONTH - Computes the serial date-time of the last day of the month for the date that is month-offset months from the date specified by the date start-date, taking into account the current date system.
• HOUR - Computes the hour for the date and/or time having the given time-value.
• MINUTE - Computes the minute for the date and/or time having the given time-value.
• MONTH - Computes the numeric month in the Gregorian calendar for the date and/or time having the given date-value, taking into account the current date system.
• NETWORKDAYS - Computes the number of whole working days between start-date and end-date.
• NETWORKDAYS.INTL - Computes the numeric month in the Gregorian calendar for the date and/or time having the given date-value, taking into account the current date system.
• NOW - Computes the serial date-time of the current date and time, taking into account the current date system.
• SECOND - Computes the second for the date and/or time having the given time-value.
• TIME - Computes the serial date-time for the given time.
• TIMEVALUE - Computes the serial date-time of the time represented by the string date-time-string.
• TODAY - Computes the serial date-time of the current date, taking into account the current date base system
• WEEKDAY - Computes the weekday number for the date having the given serial-value, taking into account the current date system and weekday-start-flag, if present.
• WEEKNUM - Computes the week number of the date corresponding to serial-value.
• WORKDAY - Computes the serial date-time of the date that is day-offset working days offset from start-date.
• WORKDAY.INTL - Computes the serial date-time of the date that is day-offset working days offset from start-date.
• YEAR - Computes the numeric year in the Gregorian calendar for the date and/or time having the given date-value, taking into account the current date system.
• YEARFRAC - Computes the fractional number of years represented by the number of whole days between two dates, start-date and end-date; according to basis.

• BIN2DEC - Makes the decimal equivalent of number.
• BIN2HEX - Makes the uppercase hexadecimal equivalent of number, with the result having num-hex-digits digits.
• BIN2OCT - Makes the octal equivalent of number, with the result having num-oct-digits digits.
• DEC2BIN - Makes the binary equivalent of number, with the result having num-bin-digits digits.
• DEC2HEX - Makes the hexadecimal equivalent of number, with the result having num-hex-digits digits.
• DEC2OCT - Makes the octal equivalent of number, with the result having num-oct-digits digits.
• DELTA - Compares two numbers for equality.
• GESTEP - Tests if the value of number is greater than or equal to that of step.
• HEX2BIN - Makes the binary equivalent of number, with the result having num-bin-digits digits.
• HEX2DEC - Makes the decimal equivalent of number.
• HEX2OCT - Makes the octal equivalent of number, with the result having num-oct-digits digits.
• OCT2BIN - Makes the binary equivalent of number, with the result having num-bin-digits digits.
• OCT2DEC - Makes the decimal equivalent of number
• OCT2HEX - Makes the hexadecimal equivalent of number, with the result having num-hex-digits digits.

• CUMIPMT - Computes the cumulative interest paid on a loan between start-period and end-period.
• FV - Computes the future value of an investment based on periodic, constant payments and a constant interest rate.
• IPMT - Computes the interest payment for a given period for an investment based on periodic, constant payments and a constant interest rate.
• PMT - Computes the payment for a loan based on constant payments and a constant interest rate
• PPMT - Computes the payment on the principal for a given period for an investment based on periodic, constant payments and a constant interest rate.

• CELL - Retrieves information about the formatting, location, or contents of the upper-left cell indicated by reference.
• ISBLANK - Determines if value refers to an empty cell.
• ISERR - Determines if value is any of the error values other than #N/A.
• ISERROR - Determines if value is any of the error values
• ISEVEN - Determines if value is an even number or refers to a cell containing an even number.
• ISLOGICAL - Determines if value contains a logical value or refers to a cell containing a logical value.
• ISNA - Determines if value is the error value #N/A.
• ISNUMBER - Determines if value contains a number or refers to a cell that contains a number.
• ISODD - Determines if value is an odd number or refers to a cell containing an odd number.
• NA - Gets the error value #N/A.

• AND - Tests if all arguments in argument-list are TRUE. The function evaluates all arguments prior to returning a value.
• FALSE - Computes the value FALSE.
• IF - Tests logical-value, and if it is TRUE, value-if-true is evaluated and returned; otherwise, value-if-false is evaluated and returned.
• IFERROR - Provides a simpler and more efficient way of trapping and handling errors.
• NOT - Computes the logical negation of logical-value.
• OR - Tests if any one or more arguments in argument-list are TRUE.
• TRUE - Computes the value TRUE.

• ADDRESS - Creates a cell address, given the specified row and column numbers.
• AREAS - Finds the number of areas designated by reference.
• CHOOSE - Selects the argument in argument-list that corresponds by position to index.
• COLUMN - Finds the number of the column(s) corresponding to reference.
• COLUMNS - Finds the number of columns corresponding to array.
• HYPERLINK - Creates a shortcut that opens a document stored on a network server, an intranet, or the Internet.
• INDEX - Locates a value or the reference to a value from within a table or range.
• INDIRECT - Locates the reference specified by ref-text and evaluates that reference to get to its underlying value.
• LOOKUP - The vector form looks in a vector for a value, and returns a value from the same position in a second vector.
• MATCH - Locates the relative position of an array item that matches a specified value in a specified order.
• OFFSET - Gets a reference to a range that is a specified number of rows and columns from a cell or range of cells.
• ROW - Finds the number of the row(s) corresponding to reference.
• ROWS - Finds the number of rows corresponding to array.
• VLOOKUP - Performs a vertical search for a value in the left-most column of a table or an array, noting the row in which the matching value is found.

• ABS - Computes the absolute value of x.
• ACOS - Computes the arc cosine of x.
• ACOSH - Computes the inverse hyperbolic cosine of x.
• ASIN - Computes the arc sine of x
• ASINH - Computes the inverse hyperbolic sine of x.
• ATAN - Computes the arc tangent of x.
• ATAN2 - Computes the arc tangent of the coordinates x and y.
• ATANH - Computes the inverse hyperbolic tangent of x
• CEILING - Computes a value that is x rounded-up, away from zero, to the nearest multiple of significance.
• COMBIN - Computes the possible number of groups of size number-chosen that can be formed from number objects.
• COS - Computes the cosine of x.
• COSH - Computes the hyperbolic cosine of x.
• DEGREES - Converts angle in radians into degrees.
• ECMA.CEILING - Computes a value that is x rounded-up, away from zero, to the nearest multiple of significance.
• EVEN - Computes x rounded to the nearest even integer, away from zero.
• EXP - Computes e^x, where the constant e is the base of the natural logarithm.
• FACT - Computes the factorial of x.
• FACTDOUBLE - Computes the double factorial of n.
• FLOOR - Computes x rounded down, toward zero, to the nearest multiple of significance.
• GCD - Computes the greatest common divisor of the one or more numbers, designated by arguments in argument-list.
• INT - Computes x rounded down to an integer.
• ISO.CEILING - Computes a value that is x rounded-up, to the nearest multiple of significance.
• LCM - Computes a value that is x rounded-up, to the nearest multiple of significance.
• LN - Computes the natural logarithm of x.
• LOG - Computes the logarithm of x to the base base.
• LOG10 - Computes the base-10 logarithm of x.
• MDETERM - Computes the determinant of the square matrix of numbers designated by array
• MINVERSE - Computes the inverse of the square matrix of numbers designated by array.
• MMULT - Computes the product of the matrices of numbers designated by array-1 and array-2.
• MOD - Computes the remainder when x is divided by y.
• MROUND - Computes x rounded to multiple, away from zero.
• MULTINOMIAL - Computes the ratio of the factorial of the sum of the values in argument-list to the product of the factorials.
• ODD - Computes x rounded to the nearest odd integer, away from zero.
• PI - Computes the value π.
• POWER - Computes x raised to the power y.
• PRODUCT - Multiplies the numeric values of arguments in argument-list.
• QUOTIENT - Computes the integer portion of the division of dividend by divisor.
• RADIANS - Converts angle in degrees into radians.
• RAND - Computes an evenly distributed random real number greater than or equal to 0 and less than 1.
• RANDBETWEEN - Computes a random integer number in the range lower-bound-upper-bound.
• ROMAN - Converts the Arabic number, number, to a Roman number according to form.
• ROUND - Rounds x to the number of digits specified by number-digits.
• ROUNDDOWN - Computes x rounded down, toward zero, to the number of digits specified by number-digits.
• ROUNDUP - Computes x rounded up, away from zero, to the number of digits specified by number-digits.
• SERIESSUM - Computes the sum of a power series.
• SIGN - Determines the sign of x.
• SIN - Computes the sine of x.
• SINH - Computes the hyperbolic sine of x.
• SQRT - Computes the positive square root of x.
• SQRTPI - Computes the positive square root of x × π.
• SUBTOTAL - Computes a value using the function designated by function-number, using the arguments in argument-list.
• SUM - Adds the numeric values of arguments in argument-list.
• SUMIF - Applies selection criteria on the values in one range of cells and sums the values of the cells in a corresponding range.
• SUMIFS - Adds the cells in a range that meet multiple criteria.
• SUMPRODUCT - Multiplies the corresponding elements in the array arguments in argument-list, and returns the sum of those products.
• SUMSQ - Adds the squares of arguments in argument-list.
• SUMX2MY2 - Computes the sum of the difference of squares of the corresponding numerical elements in two arrays designated by array-1 and array-2.
• SUMX2PY2 - Computes the sum of the sum of the squares of the corresponding numerical elements in two arrays designated by array-1 and array-2.
• SUMXMY2 - Computes the sum of the squares of the difference between corresponding numerical elements in two arrays designated by array-1 and array-2.
• TAN - Computes the tangent of x.
• TANH - Computes the hyperbolic tangent of x.
• TRUNC - Truncates x to the number of fractional digits by number-digits.

• AVERAGE - Computes the arithmetic mean of the numeric values of its arguments.
• COUNT - Counts the number of arguments in argument-list that contain numbers, and the number of cells referred to by arguments in argument-list, which contain numbers.
• COUNTA - Counts the number of arguments that are not cell references, and the number of cells, referred to by arguments, which are not empty.
• COUNTBLANK - Counts the number of cells in a specified range of cells, which are empty.
• COUNTIF - Counts the number of cells in a specified range of cells, whose values meet the specified criteria.
• COUNTIFS - Counts the number of cells within a range that meet multiple criteria.
• FREQUENCY - Calculates how often values occur within a range of values. A call to FREQUENCY shall be an array formula.
• LARGE - Computes the k-th largest value in a data set.
• MAX - Computes the largest of a set of numbers.
• MIN - Computes the smallest of a set of numbers.
• SMALL - Computes the k-th smallest value in a data set.
• STDEV - Makes an estimate of the standard deviation based on a sample, using the "unbiased" or "n-1" method.
• STDEVP - Computes the standard deviation of an entire population, using the "biased" or "n" method.
• VAR - Makes an estimate of the variance based on a sample.
• VARP - Computes the variance of an entire population.

• BAHTTEXT - Produces a string containing number formatted according to the Thai convention.
• CHAR - Determines the character that is represented by the value number.
• CLEAN - Makes a string that is a copy of string with all so-called "non-printable" characters-those with internal values in the range U+0000-001F-removed.
• CODE - Determines the numeric code of the first character in string.
• CONCATENATE - Makes a string that is the concatenation of all the strings corresponding to the arguments in argument-list, taken left-to-right.
• DOLLAR - Produces a string containing number rounded to num-decimal decimal places.
• EXACT - Performs a case-sensitive, character-by-character, lexical comparison of string-1 and string-2
• FIND - Performs a case-sensitive search using a lexical comparison for the first occurrence of string-1 in string-2, starting at character position start-pos within string-2.
• FIXED - Produces a string containing number rounded to num-decimal decimal places, using the same rounding algorithm as ROUND.
• LEFT - Extracts the left-most number-chars characters from string.
• LEN - Determines the number of characters in string.
• LOWER - Makes a lowercase version of string by doing a character-by-character conversion of string to lowercase, except as noted below.
• MID - Extracts number-chars characters from string, starting at character position start-pos.
• PROPER - Makes a lowercase version of string except that the first letter in string and any other letters in string that immediately follow a character that is not a letter, are converted to uppercase.
• REPLACE - Produces a new string that is string-1 with number-chars characters starting at position start-pos, replaced by string-2.
• REPT - Creates a string that is replication-count number of occurrences of string concatenated together.
• RIGHT - Extracts the right-most number-chars characters from string.
• SEARCH - Performs a case-insensitive search, using a lexical comparison, for the first occurrence of string-1 in string-2, starting at character position start-pos within string-2.
• SUBSTITUTE - Produces a new string that is string with one or all occurrences of old-string replaced by new-string.
• T - Retrieves the text referenced by value.
• TEXT - Produces a string containing value formatted according to format.
• TRIM - Makes a string that is a copy of string with the leading and trailing space characters removed, and each sequence of embedded spaces reduced to a single space.
• UPPER - Makes an uppercase version of string.
• VALUE - Converts string to a number.