keeping a unit in an area

ok, basicly what im asking is how do you keep a unit in a certain area when it has blink and can warp onto the walls on the side? my spell isnt blink but deos the same thing repedatively and the unit can go over everything because it is a triggered thing. i mean over huge cliffs, through as much border as you want, anywhere. if i could get the units hieght, i could do it tho but theres no such function. also regions dont work because the area is sideways and i dont want to make like 20 regions to cover the whole area with no overlap.

This should work fine

event - unit is issued an order

condition - ordered unit type = unit to be kept inside
condition - order string equal to - blink (or whatever your abilities text order string is in the ability editor)

If you dont need him to blink in the arena

action - order ordered unit to stop

Otherwise your going to have to use some things like

IF Distance between casting unit and target point of ability being cast greater than 500 or something.

Or
IF point (target point of ability being cast) is within general region equal to false
something like that. I could give you better answers but i need to know what exactly your goal is.

ok, well i have a spell called frozen feet, it actually uses an almost rangeless ward spell and the unit every like .01 seconds the unit instantly moves so much closer to the target depending on the level. the problem is instanly move target has no boundries, it just goes. even off the map. this would be so much simpler if i could use a region to cover the boundries, but the whole battle area is diagonal and regions dont really work that way. so its not i dont want him to use the abilitie in an area, its i dont want him target a not-area.