@Cal As I said, you can capture the player's input and do whatever processing you need between keystrokes. The problem I see is in managing the interaction. Can you really give any meaningful feedback to the players while they're still typing? The answer is yes, but my point is that you should do it in a way that does not become annoying.

Anyway, don't let my doubts discourage you. I don't really understand what you're trying to do, so it's natural that I can't see it, but that doesn't mean it isn't a good idea.