See step 4. Though, it wouldn't really work on its own without step 3, I'm assuming that your units will be colliding simply by walking into each other. In that case, you'd just get their velocity vectors as ( cos(Direction)*Speed, sin(Direction)*Speed ) instead of ( custom value 0, custom value 1 ) as used in the tutorial.
Oh, and in the tutorial, custom value 4 represents the mass of the unit.
I don't know, how do you get it on there?
So, you looked everywhere except the tutorials forum? Because it has exactly what you need.
http://forums.sc2mapster.com/resources/tutorials/22121-triggers-implementing-a-physics-engine/
See step 4. Though, it wouldn't really work on its own without step 3, I'm assuming that your units will be colliding simply by walking into each other. In that case, you'd just get their velocity vectors as ( cos(Direction)*Speed, sin(Direction)*Speed ) instead of ( custom value 0, custom value 1 ) as used in the tutorial.
Oh, and in the tutorial, custom value 4 represents the mass of the unit.