Reteiving a cell value of a gridview

for(int index =0;index<dt1.rows.count;index++)>
               {
                   CheckBox chkselect = (CheckBox)grdReplicate.Rows[index].FindControl("chkSelect");
                   if (chkselect.Checked == true)
                   {
                       if (res == "")
                       {
                           lblppo=(Label)grdReplicate.Rows[index].FindControl("lblgrdppono");
                           res = Convert.ToString(grdReplicate.DataKeys[index].Value);
                           ppoids = lblppo.Text;
                       }
                   }

LblMsg = Penobj._ExecuteQuery("update t_replicate_detail set MICR_CODE='" + (grdReplicate.Rows[index].Cells[8].Text)+ " ' where Replicate_ID in( '" + res + "')");