[Soukup]

these ideas dont seem to be helping you, so here's what u can do if I have the right idea of what you're trying to do.

I think that you are trying to take an viedo, and then put the video into the background. So you could see the image in the background on the big screen, and see the exact thing in the main frame.

If thats not your idea, then stop reading, cause this wont help u.

Basically, you're gonna have to render twice. First you'd take the original sequence and render that. This could also be live-video.
And then you would apply the material onto the the screen and re-render it. there is no other way to it, because if you think about it, the camera would be rendering a big screen tv, based solely on information that it had not rendered yet, because there would be stuff below the screen.

I would think that it is near impossible...... unless you wanna get real freaky and try to do some compositing in video post. By using the outputed image and then throwing it onto the same scene over the screen. This will be really tricky and I have no idea if it works, probably not. It looks like you'll have to rely on render/ re-render to finish this sequence.

hope that helped