Does anyone know enough about HyperTalk to help me solve a fairly basic problem that's giving me grief?

I need to make a countdown timer in a field, which is accurate to the second and doesn't lock up the system when it's running. In other words, no "wait" command. Any way to do this? I was thinking of something along the lines of utilising the idle handler in the stack script and basing it off the long time. My attempts at using this approach have caused problems with the accuracy though. Any geniuses with a clever solution, or shall I have to learn Realbasic? (groan)