I'm messing around with command blocks, and I'm wanting to try and make an XP vending machine. My idea is if you click a button with a Diamond in your hand, 1 diamond gets removed and you get x amount of XP.

Is this possible using command blocks? If so, what commands would I need to look at? I already know /xp myAmount @p, it's just the checking/removing of items I can't seem to get.