'dream' like request

Hey dudes,

I have a cool 'dark sky' wallpaper, and would like the light shining through the clouds to move/glow as though it really is shining through and subtly moving.  I dont have Vista, but was wondering if it's possible to make a gif or a DesktopX Object to do the job so the overall effect is like a Dream wallpaper.  If somone could make something like this, I'll....     ....erm...       ...sell you my girlfriend for a week !  (just kidding).    If not, can someone explain how I could do it myself !?  (no pun intended)

Cheers Big Ears !