I am working on a drag and drop puzzle and was wondering if someone had time to help me with a fix. I have it set up to where you have a buttons you drag that matches up with a slots. Each button can go to any slot, but the only problem is that when the slot is filled, I want to block other buttons from being able to go to that spot. As of now, even if the slot is filled, you can still drag another object to it. How can I fix this?