[Alan Anderson]

A properly-connected pneumatics system will run the compressor only when the pressure drops below 90 PSI, and will turn it off once it reaches 115 PSI. Unless you have a significant air leak, your compressor will stay off when you're not using air.

If you still want to disable the compressor completely under program control, you can do that. There are a pair of functions in the Compressor palette named Start and Stop. Just invoke the Stop function when the joystick button is pressed (and invoke the Start function when a different button is pressed so you can go back to normal operation).