using System;
using System.Collections.Generic;
using System.Text;
using Bytescout.XLS;
using System.Diagnostics;

namespace HelloWorld
{
class Program
{
static void Main(string[] args)
{
// Create new XLSDocument
XLSDocument document = new XLSDocument();

// add new worksheet
Worksheet Sheet = document.WorkBook.Worksheets.Add("FormulaDemo");

// headers to indicate purpose of the column
Sheet.Cell("A1").Value = "Formula (as text)";
// set A column width
Sheet.Columns[0].Width = 250;

Sheet.Cell("B1").Value = "Formula (calculated)";
// set B column width
Sheet.Columns[1].Width = 250;

// write formula as text
Sheet.Cell("A2").Value = "7*3+2";
// write formula as formula
Sheet.Cell("B2").Value = "=7*3+2";

// save generated XLS document into new file
document.SaveAs("WritingFormulaDemo.xls");

// open generated document in Excel (if installed)
Process.Start("WritingFormulaDemo.xls");
}

}
}

Download example source code: bytescoutxls_write_formula_into_cell.zip (2 KB)