SpotM5, if my memory serves me right, I think you had asked about playing two different movies on the rear entertainment screens correct?
I didn't have too much time to toy with the rear screens yet, but from the looks of it, the rear iDrive controller lets me select either the front dash mounted DVD player, one of the discs from the 6 disc DVD changer or the rear DVD player. That's independent for the left and right screen. The list contained a total of 8 possible DVD (player) sources. I will give this a try tomorrow as I KNOW that that's what my kids are going to ask me first about the 'TV's as they call them!!!