Barry, I have attached a sketch that is NOT a schematic but hopefully conveys my needed solution.
Think of the sound card as a free standing device with its own power supply, etc. and has as input a manual monetary contact switch/
Think of the "Driveway" Sensor/Receiver as a free standing device that has as an output a LED
I want a "black box" free-standing device that "reads" the LED emitted light. processes the On/Off status with a photologic device that "reads" the LED and then outputs by acting like a switch to the Sound CArd.