static void Main(string[] args) { OffresExcel excelDoc = new OffresExcel(@"C:\test\Copie - BX - Offres-cmd-2012.xlsx"); DataTable myTable = excelDoc.ReadWorkSheet("JAN"); int counter = 0; for (int i = 0; i < myTable.Rows.Count; i++) { if (!string.IsNullOrEmpty(myTable.Rows[i][0].ToString())) { counter++; } else { break; } } ExcelExportHelper myWriteExcel = new ExcelExportHelper(@"C:\test\BX - Offres-cmd-2012 - Copie.xlsx"); myWriteExcel.ChangeSheet("JAN"); myWriteExcel.SetCell(79, 3, "ValueAdded"); myWriteExcel.Save(@"C:\test\BX - Offres-cmd-2012 - Copie.xlsx"); myWriteExcel.Dispose(); Console.ReadLine(); }