I am trying to make it look like a child is walking through a wall. I want to gradually make her disappear. I drew a mask shape to the left of the child using the custom mask tool. My idea is to make it look like she in walking through the wall by gradually expanding the mask so it will eventually cover the whole child and she would no longer be visible. But when I try to expand the mask toward the right of the child the whole mask moves to the right no longer masking her on the left side. I though I could key frame each tiny increase in the size of the mask but that is not working.

Can I do this effect in Pinnacle?