on Button Click

As per blow code when first time click only gridview footer is display but not text shown in textbox but when 2nd time click its work.
        protected void btnAddNew_Click(object sender, EventArgs e)         {             GWMaster.ShowFooter = true;           
                ((TextBox)GWMaster.FooterRow.FindControl("txtLogRefNo")).Text = (String)Session["logmanageruser"] + "-" + (String)Session["logmanagerdepartment"] + "-" + (String)Session["logmanagerunit"];                     }
Regards,
Abdul Waheed