Keeping track of 4 button presses

I’m attempting to create a few [COLOR=Blue]very[/COLOR] simple flash games, but I haven’t been able to figure out the coding.

What I am attempting is to have 4 buttons each activated on a different keypress. Each time a user presses one of the keys, a specific animation is triggered, showing that the key was pressed. What I need to know is- how do I have flash trigger a final animation when all four keys have been pressed?

My Rube Goldberg idea: I tried making a set of dynamic text boxes that would change text, one for each button. I figured flash could run a simple string check (like in the basic password tutorial here) and if they all proved true it could goto and play the next scene or another MC. BUT- It seems to only check at the beginning of the movie, and if I attached it to onEnterFrame, Flash would have a cow about my syntax!

Any ideas? It must be pretty simple- but it requires more finesse than I have.

In short: 4 buttons, each triggers an MC, after pressing all four individually, go to next scene.

Thanks!