fade transition

Right now I'm fading a picture from one frame to another with this code

toploader.faderate = 4;
var toploader_interval:Number = setInterval(topdrive, 15, toploader);
function topdrive(toploader:MovieClip):Void {
toploader._alpha -= toploader.faderate;
if (toploader._alpha<=0) {
clearInterval(toploader_interval);
toploader.removeMovieClip();
toploader.attachMovie("top1", "toploader", 1);
toploader._alpha = 100;
}
}

Ok so toploader is always the image from the frame before. It first fades away revealing the new image underneath it. Once it fades completely the contents are erased and replaced with the new image so there two instances of the new image, one on top of the other. Then when you move to the next frame the bottom instance changes to the new image and the cycle repeats.

What id like to happen instead of a generic fade is a starwars-esque swipe fade transition. Is there any easy way to do that with this code?