Jitter flickering

Hey, I've got this patch, where movie A is playing, then when the sensors see someone moving, movie B will play. Now my problem is the way I set it up, when movie B plays, movie A is still in the background, and it flickers annoyingly. Is there a way in making movie A stop while movie B is playing and then when movie B stops movie A is back to playing? so that would stop the flickering.

I have attached the max patch.

Thanks in advanced.