Fade in fade out rollover

I need help making a banner that fades out one image and increases visibility on another. Kind of like one of the Kirupa footers i saw on one of the tutorial pages. Here is the link. http://www.kirupa.com/developer/swift/wireframe.asp . As you drag to the right one image fades out and another becomes visible, Can anyone help me out with this actionscript?

try this out:

This is exactly what i was looking for! Thanks!

Great! Pretty nice code, wish I could come up with stuff like that. It comes from the Friends of Ed book: Flash ActionScript for Designers. Quite a good book for a neophyte like me.