Collision Detection with GUI?

[PoP_PiP]

Hello, I was wondering how most people go about detecting cliffs / doodads with triggers?

For example, with certain spells that use timers to move a unit.

 

[iplaystarcraft]

not too sure what your asking but my guess is they used reigions...

 

[PoP_PiP]

Regions sound like a possible solution, I'm going to try to see what I can do, but basically, what I mean is:

Event
- "Repeating Timer" expires

Action
- Move unit 50 towards angle of "Target Destination"

How would you detect a cliff or doodad and tell the trigger to stop?