OOP: balls that bounce off each other?

I have a simple ball class where it bounces and such and stays on the stage based on boundaries. right now im using a for loop to attachMovie(“ball”,…) in my main fla file

which is basiclaly my movieclip that has the AS 2.0 class pointed to it.
It bounces fine using the tutorial on Kirupa(by senocular?)

i want these balls to bounce off each other too? any idea on the approach.