[Greg McKaskle]

Keep in mind that the way you wrote it, the optional code is producing the constant, but you are still calling the relay function regardless of what the buttons do. In fact you are calling it twice. Try putting the subVI inside of the case statement too. That way if button one, you send the one value to the relay. In parallel, if button two, send the other command to the relay. If neither button, don't do anything to the relay.

Greg McKaskle