Detect screen change and send serial signal through usb output to be registered by second computer.

It is a two computer setup. I will be forwarding the video output of one computer(Computer A) to another (Computer B). On Computer B I will have the video forwarded from Computer A full-screened. I need a program that runs on Computer B and that will detect changes in the center of the screen, say a 64x64 pixel window in the center, and then upon detection send a serial signal that mimics a mouse right/left click through a usb output that can be recognized by Computer A. Should go something like this > program is started on Computer B > press button on Computer B> gets the current state of the screen by running a checksum on the array or however you choose to do it > then monitor the video input until it changes > sends serial signal through usb output on Computer B that mimics mouse right/left click > clears all values and waits for button press command to run again. There are other small things I would like to add but those can be discussed.