Unit close to a wall?

Is there any way to execute an action if a unit comes X range close to a wall/cliff?

I really don't want to create regions for every wall, as it's quite many, not talking about walls that are not rectangular.

EDIT: Come on. I've seen some amazing stuff being done here at wc3c(such as custom lights, saving & restoring a hero)..

This shouldn't be impossible. Or is it?

Only way I've been able to come up with is via the use of regions which are adjacent to any non-walkable regions. There's really no way to access the pathing through triggers or check its conditions.

-Nicodemus

What do you mean by "adjacent to any non-walkable regions."?

That I have to use regions after all? That sucks.

Hmm, the cliifs/walls are models, right? Is it possible to use that model on a unit and then use the "Unit comes within X of unit"? Or? I'm desperate :/

iif you are desperate, you can put a series of invisible flying units by the walls, and check range with the units