Building structures around a unit

i need help:

i want that structures can't be built in a circle of about 300 around 4 units that change during game.. but i aint the faintest idea how to do it :(

the normal triggers dont allow that :(

Yes they do, you have to create a unit at a point of distance with polar offset from another point.

Well, the way I see it, you could make a trigger that cancels construction of a building if it starts within range of that unit. Or, you could create modelless units around the unit so that a player is unable to build there. Or, if the unit is stationary, you can place terrain that's unbuildable around it.