I'm a little confused about what exactly you are doing, but I'll make some assumptions.
If you are using an UpdatePanel to do your AJAX postbacks, you can use an UpdateProgress control to show something after a specified number of time (e.g., 2 seconds).
Supposing you have an UpdatePanel called
, your UpdateProgress control would look something like this:
<asp:UpdateProgress runat="server" AssociatedUpdatePanelID="upSearch" DisplayAfter="2000">