I’m currently experimenting with using Blender as a compositing program. What I want to do (eventually) is move a model behind a person in the scene. This is like the scene in Star Wars: A New Hope that Industrial Light and Magic added where Han walks behind a CG jabba the hut. In order to do this, I have to animate an alpha mask to cover the model that moves behind the character. My problem, however, is that I can’t get the movie shown in the display window to advance frame by frame. For example, if I set a movie as a texture for a plane, I want to be able to see the frames advance in the display window. I thought that as I advanced the frames in blender, it would automatically do this, but it doesn’t seem to work. Am I sadly mistaken, or is there another way? Thanks for your enlightenment!
The old Elysiun “Search” saves the day again… 
Thanks!