Back up cam auto turn on

So I know I can use a relay to take power from the reverse lights to turn on a back up camera and turn it off when the car is out of reverse. The difficult part is automatically switching the source of my monitor. I have a lcd with 3 inputs that change via pressing a source button to scroll through them. It starts on the VGA input from my computer then goes to input 1 and then input 2. I can make a relay that would pulse once when the reverse lights which could then trigger another relay to "press" the source button once. But then I need to press it twice when I am out of reverse to return to VGA input. How can I get it to pulse twice (about a second or so inbetween pulses) when I leave reverse? I have tried drawing up a bunch of relay designs but I dont think it is possiable... I think I need some sort of circuit or something. Anyone have any idea how I can solve this problem?

It all depends on the other hardware Some multi-source monitors will have a serial connector that will allow a wired remote control A serial port on the computer could also be used by an application to open a video capture window when the reverse lights are on

I have a lilliput 7" lcd screen. I have some extra parts like a controler board and stuff. I could look around but I dont think there is anything that could do it...