Highlight Button on Keypress

I need to make a simple virtual keyboard gui program in C# that functions as a spell checker. Not as in, I click the "s" key and it inputs "s" into the text box; but rather, while I'm typing, the on-screen keyboard highlights each letter as I press it. It's supposed to be for people who are learning how to type so they don't need to look down at their keyboard.

Can someone familiar with C# help me figure out how to make a button (or if you can suggest something better than a button) highlight upon keypress? To be more specific, can you point me in the right direction to get an event handler in place for each button to "highlight" for every keypress on the keyboard? Once I get that, I think I can get the spell-checker coding out of the way.

I'm using Visual Studio. Here's a screen shot. Both text boxes are rich text boxes, the top is set to "read-only", and that is the text that needs to be entered. The "keyboard" underneath is just composed of buttons.

Thank you in advance!