Nav GPS Monitor (HELP)

OK, maybe this has already been discussed. I just recently purchased a new 2005 Armada, I have the back up cam, the DVD player, and the navigation system, etc. What I would like to know, if there is a way I can connect the DVD player into the NAV screen so DVD's can be seen on that screen as well. That way my wife doesn't have to sit in the rear seat to watch DVD's while we are on trips. Is there some sort of switch that can be wired in so that I can switch from NAV to DVD ? Any help would be appreciated.