Picture combining in Flash help

What I want the user to be able to do is to erase parts of the top image, revealing some of the bottom image, thus creating a unique mixture of both the top and bottom image combined.

Ex. say i had two pictures. one of a dog’s face and one of my face.

the dog picture would be on top of my picture

I would erase parts of the dog picture revealing pieces of my face.

in the end I would have a new picture, one that is a mixture of the two
original pictures.

I was wondering if there was a way to do this in flash?