Rear Sound Question

I have a 04 LE with the Bose system, factory rear dvd, Kenwood 4100 nav unit. When the headphone/speaker button is pushed to turn the speakers on, it turns the dvd off. Does anyone know if it is possible to not turn the dvd off when the speakers are on? The place that installed the nav unit isn't sure if it can be done or not. The video is split so it can be watched up front, but there is no sound in the back unless the headphones are used. I have sound in the front from using the aux input. Any help would be much appreciated.

Bruce