Async - AJAX AutoCompleteExtender

I'm using a AJAX toolkit AutoCompleteExtender control on a textbox.  The webservice associated with the control uses cached data from a database query.  It performs great after the data has been cached.  The query itself takes over a minute to complete.  What I'd like to do is:
Load the page with the AutoCompleteExtender control disabled.   Asynchronously query the database and cache the data allowing user to enter/submit form data without the help of the AutoCompleteExtender. Enable the AutoCompleteExtender after the data has been cached (visual indicator on page letting user know of AutoCompleteExtender status would be nice).  I'm caching the extender data using a HttpContext.Current.Application object (it's static reused across multiple user sessions) which is null in th ...