Is it possible to fade-out a slideshow?

A conceptual inquiry:

I’m planning on creating a slideshow with cross-fades.

I’ll be placing this as a .swf (as a movie clip) in another .fla .

I’d like to be able to click a button in this new .fla and have the slide-show MC fade out independently of where this MC is in its timeline.

I’d also like to be able to do this on one frame (i.e., without having to add extra frames/outtros).

Since I’m basing this on a click of a button, I’m assuming I can’t use an onClipEvent (enterFrame) {} as a loop for this.

Is there AS that will somewhat slowly, smoothly change the alpha on an MC or is there a way to create a loop that won’t run so quickly as to “snap” the alpha from 100% to 0% faster than the eye can see?