I think I'm doing this right, but I don't know, you tell me.
It's ok you guys, I solved my problem. All it took was a change in the expressions. Still there are some other problems that have turned up. Here's a link to the original project, and a link to the fixed version. The Calculator version 1The Calculator version 2
A problem that's really a technical issue I wish to address is that the program can't do multiple operations at once from the buttons, to do this you need to press equal every time you want to do the operations in sequence.