Using MovieClip methods in custom class

I’ve got a custom class (using AS2) that mostly does things like set the score and level of a game, as well as sets the player’s lives on the screen. I need to unload and attach MovieClips within the Lives control function, which require those methods from the MovieClip class.

I don’t think I need to extend this class from the MovieClip class, I think I need to import the class somehow. I don’t know the path though…something like mx.MovieClip.* or something?