Motion or After Effects Masking question
 

I'm working on a comp in which a sign is matted out of a handheld shot and replaced with a video element.

I've gone in and painstakingly matted the sign for the whole shot, but I'm having trouble getting the video replacement to look good because I have to keyframe it to follow the matte.

Is there an easier way to do this? Is there some way to make my matte's keyframes and my replacement image's keyframes be the same? I have both Motion and After Effects CS3. Any tips would be appreciated.

Edit: Wrong forum. Sorry. Can someone move this please?