How Do I Use A Waiting Popup For Grid Grouping Control ?

<script type="text/javascript">
        Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(BeginRequestHandler);
        Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler);
        function BeginRequestHandler(sender, args) {
            Popup.ShowPopup();
        }
        function EndRequestHandler(sender, args) {
            Popup.HidePopup();
        }

        //Set GridPager width corressponding to GridGroupingControl
        Sys.Application.add_load(function () {
            var grid = $get('<%=Me.GridGroupingControl1.ClientID%>' + "~OT~");
            var pager = $get('<%=Me.GridPager1.ClientID%>');
            pager.style.width = (grid.clientWidth - 7) + "px";
        });
    </script>

<Syncfusion:WaitingPopup ID="WaitingPopup1"   ClientObjectId="Popup" runat="server" Alignment="MiddleCentre" AutoFormat="Rollers"
     Height="50px" Width="125px" DisabledBackgroundColor="221, 227, 238" DisableOnShowElementID="GridGroupingControl1" Direction="LeftToRight" TimeSpan="50">
 </Syncfusion:WaitingPopup>