C# - Automatically Hide A Modal Popup Control?

I have a model pop extender control like:

<cc1:ModalPopupExtender ID="basketPopUp" runat="server"
PopupControlID="Panel1"
PopupDragHandleControlID="PopupHeader"
Drag="true"
BackgroundCssClass="ModalPopupBG"
TargetControlID="Panel1">
</cc1:ModalPopupExtender>
<asp:Panel ID="Panel1" Style="display: none" runat="server">
<div class="PopupBody">
<b>Test</b>
<br />
</div>
</asp:Panel>

What i want is to show the popup for 5 seconds and HIDE it AUTOMATICALLY after this period of time.

I've tried this, but, running on the server side, of course it is not working:

public void showAndHidePopUp()
{
basketPopUp.Show();
System.Threading.Thread.Sleep(5000);
basketPopUp.Hide();
}

Do you know how to hide it in a proper way?

Edit:

For announcementes i've decided to use jGrowl-> [URL] and not ModalPopUp Extender.