Show dialog when processing data

[WojTec]

Here is pseudocode which demonstrate what I want to tell:

Delphi-Quellcode:

CreateAndShowDialog();

MakeSomeTaskWhichNeedManyCPUTime()

DestroyDialog();

Dialog contain animated marquee. Normally I'm, creating it, showing in modal mode and then call Invalidate(), but then Windows don't refresh animation. How to show this dialog during data processing and do not lock it update?