ASP.Net AJAX UpdatePanel: Block Page and display Progress using ModalPopupExtender

Solved problem using ModalPopupExtender ajax control.

  <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>

    <asp:Panel ID="panelUpdateProgress" runat="server" CssClass="updateProgress">
        <asp:UpdateProgress ID="UpdateProgress1" runat="server" AssociatedUpdatePanelID="UpdatePanel1">
            <ProgressTemplate>
                <div>
                    Loading...
                </div>
            </ProgressTemplate>
        </asp:UpdateProgress>
    </asp:Panel>

 <cc1:ModalPopupExtender ID="ModalProgress" runat="server" TargetControlID="panelUpdateProgress"   BackgroundCssClass="modalBackground" PopupControlID="panelUpdateProgress" />


and CSS 

.modalBackground     
 {
  background-color: Gray;     
  filter: alpha(opacity=50);     
  opacity: 0.50; 
 }