Tracking help

[bumpsetspike]

I am totally new at AE and I desperately need help.  I made a video of someone holding a picture frame and moving it around in front of their body.  I made a second video with the exact same scene minus the person.  I want to subtract the footage inside the picture frame so that it just displays the background from the 2nd video.  This way it will make it as if the picture frame sees through the body. 

I know how to use four point perspective tracking on the frame but I don't know how to use it to cut out that portion of the first video.  Any help would be greatly appreciated!

[joojaa]

make the frame white, everything else black then use that as a coposition insdie the other composition, then place the revela layer below thei band white layer, and then in the revealable layers comp mode section choose track matte, luma wgatever your comps name. done (make sure the layer on op is hidden.)

[bumpsetspike]

Thanks for you response, I just have one dumb question:  How do I make the frame white and everything else black?

[joojaa]

hide the layer your tracking?