Need help with flash variables! ! !!

Currently i am screwing around in flash with variables. Like if you touch this MC your health will drop which is the number displayed in the top left corner of my flash. THe only problem is, how do i get the movie to play a certain frame when the health variable in the dynamic text box hits 0. I’ve tried a couple of codes but they didn’t work. Could people please help by posting their actionscript to solve this problem and explain the stuff i should have done in my flash to make it work.

P.S sry if this is too much to ask.