I am developing a MS-Word addon in which my code has to get access to the letters the user is entering through the keyboard.
private void ThisDocument_Start
Microsoft doesn't expose a key down event natively, but there's a workaround.
I implemented keyboard checking with help from the article linked below:
http://www.switchonthecode.com/tutorials/winforms-accessing-mouse-and-keyboard-state
This gives you a static method called IsKeyDown, implementing and invoking a delegate you can subscribe to should be fairly straight forward.