Updatepanel Inside Modalpopup Not Working?

I'm doing a website with Ajax and Framework3.5.

I have a update panel inside a modalpoupextendar which is in another update panel.

When user need to click the button in the parent update panel the modal popup will appear,

then in the popup if user click a button there I Need to show some text in a user control which placed in the panel.

See the html tag and tel me any solution. Its not working for the first click its working in the second click only.

Code:

<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional" ChildrenAsTriggers="False">
<ContentTemplate>
<asp:Button ID="btnHidden" runat="server" Text="Button" />
<cc1:ModalPopupExtender ID="ModalPopupExtender2" runat="server" BackgroundCssClass="modalBackground"
BehaviorID="popup" DropShadow="true" PopupControlID="pnlUpdate" CancelControlID="btnNo"
TargetControlID="btnHidden">
</cc1:ModalPopupExtender>
<asp:Panel ID="pnlUpdate" runat="server" CssClass="modalPopup" >
<div>
<asp:UpdatePanel ID="UpdatePanel2" runat="server" UpdateMode="Always">
<ContentTemplate>
<div>
<uc1:Feedback ID="Feedback2" runat="server" />
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger controlid="btnTest" eventname="Click" />
</Triggers>
</asp:UpdatePanel>
<asp:Button ID="btnTest" runat="server" Text="Test" onclick="btnTest_Click" />
<asp:Button ID="btnNo" runat="server" Text="Cancel" /></div>
</div>
</asp:Panel>
</ContentTemplate>
</asp:UpdatePanel>
</asp:Content>