Any way to detect when a unit starts targeting a spell?

Is there a way to detect the moment a player clicks a unit's ability button to begin targeting the unit's spell? I'd like to be able to detect that and then create a customized spell area-of-effect projection (like you see in a normal game, with different patterns for Human, Night Elf, Orc, Undead that lay over the terrain and turn all trees and stuff in their path green).

Come to think of it, is there any way to mimic the effect of that in-game selection region?

I'm pretty sure that's a no on both counts. There is no order when the button is clicked (unless the ability doesn't target, but then it enter's cooldown and does effects) and to even start trying to simulate the AoE target thing you would need mass trackables. Not viable.

You could just import new .blp's over the current AOE targeting textures.
That's a lot easier and manages an identical effect.

Figured so.

It won't help me to do the texture swap--what I was trying to do is make a targeting area other than a circle, like a cone or a quad of circles that really show you where one of my spells is going to target (it relates to the point you cast it and the caster, but it's not just a single straight line).

Thanks anyway, +rep both.

Capt. Picard