Wait & Final Dialog while Creatig Exchange Mailbox

I have created some code to create a ad-user and its mailbox. Because the creation process took a "long " time, I would like to show a "waiting dialog" to the user and after the process a conclusion/error page.

how do I program this? I tried AsyncPageTask fromhttp://msdn.microsoft.comand a lot of other stuff.
But the problem is always the same: the page is blocking, while the process has been ended.

so what do I want: #1 some form stuff, #2 user clicks on the button -> waiting page #3 conclusion or error page... a MultiView Object would be fine.

Could someone help me? Thanks in advance! have a nice dayI am using the OnClientClick Handler of an ASP-Button