Exit an executable using a four digit string

ello peeps, I am currently completing a flash touchscreen project and have almost finished but come up against a problem that seems so simple yet I just can't get my head around it. Okay, I've created an executable that I need to close when a user enters a four digit string. The default is to exit on Esc, however, this makes it too easy for a user to be able to close the executable and then have access to the computer. I'm sure that I did a similar thing whilst a Uni (but it was oh so long ago), please help!

Thanks in advanced

use the Key class and add a listener,
not sure right now if dynamic text has a listener for change text events.
anyway in that listener, check if the user press Enter, then