Cool animated line drawing

hello, I am looking for a way to create an animation in flash like this link:

ok, so maybe this animation is not that cool. But line ‘draw-ons’ like this are quite common and I cannot find an easy way to do this in flash. I have tried masks, but (as far as I can tell) the line path is too complex for a mask. I have tried animating it using shape hints, but flash just gets hopeless confused as to how I want the line to animate on. I could export this as an swf out of AfterEffects, but the file size seems way too big for what the animation is. I have begun to realize that maybe this type of animation is often achieved using actionscript.

I am looking for a step-by step explanation of doing this in actionscript. I’m an actionscript beginner, but ready to learn! I am using flash cs3.

thank you for your help and consideration,

Jeff Lebowski