VGA projector using Mac book problem

Hello!
I use djing with Serato software on a13.5inch Mac book. I also use the Music Video part of it., using it with a VGA projector works just fine.
However a Focau projector connected to VGA powered adaptor that has a cat5 cable expands the control window on the mac which makes it too big.
What are some of the solutions I can try?
Can you please help me this.
Thank you.
