Handling text input -- not in a textfield

I am writing a class that will handle text input using a keyboard event attached to the stage (or it could be attached to a movieclip or something else). It will have many applications, but to give you a picture of something it might do, it could be used to input “cheat codes” where you type something and it updates a string variable. Then when the string matches some code it calls some function (and in this instance it may be annoying or impossible to use a textfield for this).

It is pretty easy to take all the keycodes and convert them into text (or program whatever function they serve, like backspace), but it is also relatively time consuming. Is there an easier way, or does anyone know of someone elses class out there that does something similar?