Bounce Collision Between Movieclip

Hi, this is my problem: In the stage I have 3 or more boxes and, following some tutorials, I am succeed to create gravity and collision with the stage margin. But my target is make a realistic bouncing between the boxes: when I drag and throw a box against another box, I want to see the boxes that bounce in reverse direction like in reality.

I hope of to be succeed to explain my problem.

Here my file to see the actionscript code: http://tredimental.altervista.org/bounce_fla8.fla

Thank you!!!