Export data from datagridview to Excel in C# with Column position Mistake

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C#

Hi everyone!
When I export data from datagridview to excel in c# i have a mistake!
The column calculation (it's not in database) I put at column last in datagridview. I can see it in interface, but when I used command export data to excel then the column calculation at the column frist. Can you help set it at column last? Plese .
This is my code to use export to excel.

static public bool exportDataToExcel(string caption, DataGridView grv)
        {
          
            bool result = false;

            Excel.ApplicationClass xlApp;
            Excel.Worksheet xlSheet;
            Excel.Workbook xlBook;
          
            object missValue = System.Reflection.Missing.Value;
    
            xlApp = new Excel.ApplicationClass();
            xlBook = xlApp.Workbooks.Add(missValue);

             xlSheet = (Excel.Worksheet)xlBook.Worksheets.get_Item(1);
          
            xlApp.Visible = false;
            int socot = grv.Columns.GetColumnCount(DataGridViewElementStates.Displayed);
            int sohang = grv.Rows.Count;//dt.Rows.Count;//
            int i,j;

            SaveFileDialog f = new SaveFileDialog();
            f.Filter = "Excel file (*.xls)|*.xls";
            if (f.ShowDialog() == DialogResult.OK)
            {

              
                xlSheet.get_Range("B1", Convert.ToChar(socot + 65) + "1").Merge(false);
                Excel.Range caption = xlSheet.get_Range("B2", Convert.ToChar(socot + 65) + "1");
                caption.Select();
                caption.FormulaR1C1 = caption;
				
                caption.HorizontalAlignment = Excel.Constants.xlCenter;
                caption.Font.Bold = true;
                caption.VerticalAlignment = Excel.Constants.xlCenter;
                caption.Font.Size = 16;
                caption.Font.Name = "Arial";
                caption.Font.ColorIndex = 3;
               
				
                caption.Interior.ColorIndex = 6;
                caption.RowHeight = 25;
     
                Excel.Range header = xlSheet.get_Range("B2", Convert.ToChar(socot + 65) + "2");
                header.Select();
                header.HorizontalAlignment = Excel.Constants.xlCenter;
                header.Font.Bold = true;
                header.Font.Size = 12;
                header.Font.ColorIndex=2;
                header.Font.Name = "Arial";
                header.Interior.ColorIndex = 25;
               
                for (i = 0; i<socot ; i++)
                {
                    xlSheet.Cells[2, i + 2] = grv.Columns[i].HeaderText;
             }
                for (i = 0; i < sohang; i++)
                    for (j = 0; j < socot; j++)
                    {
                       
                        xlSheet.Cells[i + 3, j + 2] = grv.Rows[i].Cells[j].Value.ToString();//dt.Rows[i][j].ToString();//;
                        ((Excel.Range)xlSheet.Cells[i + 3, j + 2]).Borders.ColorIndex = 25;
                        ((Excel.Range)xlSheet.Cells[i + 3, j+2]).VerticalAlignment = Excel.Constants.xlCenter;
                        if (j == 0 || j == 1 || j == 7)
                            ((Excel.Range)xlSheet.Cells[i + 3, j + 2]).HorizontalAlignment = Excel.Constants.xlCenter;
                        if (j == 3)
                        {
                         ((Excel.Range)xlSheet.Cells[i + 3, j + 2]).HorizontalAlignment = Excel.Constants.xlLeft;
                           
                        }
    ((Excel.Range)xlSheet.Cells[i + 3, 7]).WrapText = true;
 
                    }
                
                for (i = 0; i < socot; i++)
                {
                    ((Excel.Range)xlSheet.Cells[1, i + 1]).EntireColumn.AutoFit();
              
                }
              
                //save file
                xlBook.SaveAs(f.FileName, Excel.XlFileFormat.xlWorkbookNormal, missValue, missValue, missValue, missValue, Excel.XlSaveAsAccessMode.xlExclusive, missValue, missValue, missValue, missValue, missValue);
                xlBook.Close(true, missValue, missValue);
                xlApp.Quit();
                
               
                releaseObject(xlSheet);
                releaseObject(xlBook);
                releaseObject(xlApp);
                result = true;
            }
            return result;
        }