Accessing variables inside other movieclips

I’m currently learning OOP through Sen’s information here at Kirupa, and I’ve decided to try out his “creatures” exercise mentioned in his Best of Senocular thread…I still have a bunch to learn, but I wanted to go ahead and ask a question for a problem I am having right now.

The situation is a random number of sprites are created, and they move around the stage, interacting. They all have a certain amount of “health,” defined as a variable in a MovieClip prototype applied to the MC. When they hit, I want their health to go down a little bit, so how can I access a particular MC’s “health” variable while I’m outside of the MC itself?