The dealer won't make the modification because legal requirements do not permit them to do this. I understand from someone I talked to that there is a switch located in the handbrake or activated by lifting the handbrake. If I lift the handbrake very slightly, the DVD will display video and sound (even with vehicle in drive and moving down the road), but if I lower the handbrake, the video is blocked and only audio plays from the DVD, and NAV map is displayed.