how to check if a column is empty in excel sheet during import

Hi, i am importing data from excel and want to check the empty columns. below is the code i have got. 
Microsoft.Office.Interop.Excel.ApplicationClass clsExcel = null; Microsoft.Office.Interop.Excel.Workbook clsWorkbook = null; Microsoft.Office.Interop.Excel.Worksheet clsWorksheet = null; // open the template... clsExcel = new Microsoft.Office.Interop.Excel.ApplicationClass(); clsExcel.Visible = false; clsWorkbook = clsExcel.Workbooks.Open( @"D:\Vidya\ALL PROJECTS\Sharavana Bhava\Mailer\omsharavana_WF_newsletter\Application\trunk\email_list\sample.xlsx", 2, false, 5, "", "", true, Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "", false, true, 0, false, true, Microsoft.Office.Interop.Excel.XlCorruptLoad.xlNormalLoad); // get worksheet... clsWorksheet = ((Microsoft.Office.Interop.Excel.Workshe ...