Splitter for Projector going to seperate rooms.

The Problem: Need to be able to connect a computer from room A or Room B to Projector in the viewing room. There never will be a time when

a computer is hooked up in both rooms.

Projector is in the viewing room mounted to the ceiling which is 20 feet High.

Room A to viewing room has 100' VGA cable

Room B to viewing room has 50' VGA cable.

Looking for a splitter that allows me to tie both cables into the projector.

I have tried a Monitor cable (VGA splitter cable HD15 F/M/M) but when it is connected to the projector from Room A

it gives a double image. If  I connect either cable directly to the projector the image is perfect.

Any Ideas? I don't like the idea of using a ladder to switch cables any time that I need to change room locations.