Is there a Windows API function to get the "fading window to sytemtray" effect?

I've written a resident chat app similar to microsoft messeger, so that its icon is at system tray and if you ask the app to close, it just fades out to that icon.
To get that fading I've used a timer and "MoveWindow" function.
The effect is quite nice but,
does anyone know if is there a Windows API function to specificly get that "fading window to sytemtray" effect?
I've seen it in several Microsoft programs and I was wondering if there is already that API.