Buttons in visual studio .net

At the momenet, we are extending our gui calculator made in visual studio .net, originally it could only input numbers by typing them in screen, now we are required to be able to make buttons as well.. I'm not sure how to make when the buttons are pressed, display onto screen. We received a pdf document showing how, but i think it's a bit complicated. Could someone help?

One thing, I'm also implementing base convesions, i.e. hex, octal so on. i want for example if i press decimal, a, b,c etc buttons are disabled, how do u do this?

thanks

anyone please?