Display "Process Completed" Message in UpdateProgress.

Hello

I've Image button in my GridView and when user clickling this ImageButton opening Panel with AjaxModalPopUp Extender.

In ModalPopUp I've UpdateProgress. 

User clicking ok button then UpdateProgress starting display a gif. 

I want to display "Completed" message at the end of OnClikEvent. 

When I debugging, simply watching in debugger that Label control changing message but in the browser doesnt change anything.

Any help?

//aspx<tr style="height: 30px;"><td><asp:UpdateProgress ID="updProgress" runat="server" DynamicLayout="true" AssociatedUpdatePanelID="UpdatePanelModalPopUpButtons"><ProgressTemplate>                                                            <div class="progress"><asp:Label runat="server" ID="LabelProgress" Text="Talep gönderiliyor." ></asp:Label></div><div class="progress"><asp:Image runat="server" alt="" style="vertical-align: middle;" src="/Images/ajax-loaderimg.gif"  /> </div></ProgressTemplate></asp:UpdateProgress></td></tr><tr align="center"><td><asp:UpdatePanel runat="server" ID="UpdatePanelModalPopUpButtons"><ContentTemplate><asp:Button ID="btnAddToCart"
                                                                runat="server" Text="Evet"
                                                                OnClick="ButtonSendStoneRequest_Click" Width="100px"
                                                                OnClientClick="this.disabled=true;" UseSubmitBehavior="false" /><asp:LinkButton ID="btnClose" runat="server" Text="Kapat" Width="100px" ForeColor="Navy" OnClientClick="return HideModalPopup()" /></td>                                            </ContentTemplate></asp:UpdatePanel></tr>
//cs
 protected void ButtonSendStoneRequest_Click(object sender, EventArgs e)
    {        
        btnAddToCart.Enabled = false;
//sending email
//
//
        btnAddToCart.Enabled = true;

        
        ((Label)updProgress.FindControl("LabelProgress")).Text = "Whatever you want it to say.";
        System.Threading.Thread.Sleep(5000);
        ModalPopupExtender1.Hide();        
    }