well first of all an Location Variable is only an Point you need to do something like this
make an region var named[name of your region]
make an point var named[name of your point]
in my example the region is named AreaofEffect and the point Temp_point
Trigger:
Set Temp_Point = (Target point of ability being cast)
Set AreaofEffect = (Region centered at Temp_Point with size (250.00, 250.00))
the size must be AOE of the cluster rockets in your exemple
don't forget to clear the leaks with this actions
As far as I know, Cluster Rockets' AOE is a circle, not a rectangle like your region.
I only think you can do it by picking all units in 250 range of your point, if you want it to affect units. Otherwise, do stuff in 250 radius of the point.
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.