How would you make an Anti Walling system?
Like, in a defence. Units are walled in, so they break the wall. (Units blocking them in) How would you make it so units do that?
They do it automatically. It's part of the Order->Move to Location command I think. Just try ordering them to move to a location and walling, you'll see.
Alright, I'll give that a try. Thanks.
And where is this Moderation Box? Everyone says bottem left corner, but I dont see it... I might just be retarded. Can you send me a screenie of where it is?

When the computer unit moving realizes there's no way to get through, he'll automatically turn into "stop" status. If it's hostile, then it'll attack building's by itself.
(considering it's not a spellcaster/worker)
Be sure they're not constantly ordered to move.
It's here: