[Alan Anderson]

How would you want it to work? There are a number of possibilities. My preference might not be the same as yours. Until you pin down the details, I'm reluctant to give you a specific solution.

So tell me a story. Imagine that it's working as desired. Describe what the driver does in order to shift gears, and explain what happens on the robot as a result. Make sure you detail the action that occurs when a button is pressed, and again when the button is released. If anything special takes place when the button is pressed and held, let us know that too. If the same button does different things at different times, make sure you explain why.

After I know in sufficient detail what you want it to do, I can help you learn exactly how to program the robot to do it.