I have tried with
protected void gridCustomer_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
DateTime olddate = Convert.ToDateTime(e.Row.Cells[9].Text); /*Error : String was not recognized as a valid DateTime.*/
DateTime today = DateTime.Now;
if (olddate > today)
{
Label status = (Label) e.Row.FindControl("lblStatus");
status.Text = "AutoHold";
}
}}