object to position to follow mask

i can't seem to figure this one out. i hope you are able to do it. basically what i want to do is make a mask on a layer (keep it simple...a square mask), then i want a separate object (a photoshop file) to travel on the path of that mask (without having to eyeball it and set the keyframes myself obviousy). i know when you draw a motion path, it converts it to keyframes. that's not what i'm looking for, i want to be able to either convert a mask's path to keyframes, or just tell the object to follow the path of the mask (this would be especially helpful if the mask were to animate...the object would continue to travel based on the mask.

hope that was clear.

thanks