Get Index of Column Name to Map with DataTable C#

I want to import an excel data in database. I have an excel which gets updated by team every month and they add new column with name "Jan data format" (current month name + "data format"). which gets added after the last month column.

DataTable dt = new DataTable();
            dt.Columns.Add("SOURCE");
            dt.Columns.Add("DUMMY CODE");
            dt.Columns.Add("CUSTOMER CODE");
            dt.Columns.Add("STK_CODE");

            DataRow row;

            while (((Microsoft.Office.Interop.Excel.Range)wks.Cells[rowIndex, 1]).Value2 != null)
            {
                row = dt.NewRow();
                row[0] = Convert.ToString(((Microsoft.Office.Interop.Excel.Range)wks.Cells[rowIndex, colIndex]).Value2);
                row[1] = Convert.ToString(((Microsoft.Office.Interop.Excel.Range)wks.Cells[rowIndex, 2]).Value2);
                row[2] = Convert.ToString(((Microsoft.Office.Interop.Excel.Range)wks.Cells[rowIndex, 3]).Value2);
                row[3] = Convert.ToString(((Microsoft.Office.Interop.Excel.Range)wks.Cells[rowIndex, 4]).Value2);
                index++;

                rowIndex = 2 + index;
                dt.Rows.Add(row);
            }

Here row[1] = Convert.ToString(((Microsoft.Office.Interop.Excel.Range)wks.Cells[rowIndex, 2]).Value2); i'm using column index. How to use Column Name in place of column index?