Making a Trigger Detect an Issued Order?

[Griffen25]

hey peeps,

My Problem:

I'm making a use-able thorns aura with a 250% dmg return. I'm new to custom maps however I've managed to create a dummy unit activate a buffed thorns aura for 5 sec then die.
However i want the triggering hero to channel the thorns aura, and if he so chooses, to stop channeling. So i made a dummy spell using tranquility. However the problem remains that the hero is still able to activate the ability, and just move/attack/stop still with the aura.

My Solution:

I've been fiddling with a trigger to tell when the triggering unit has been issued an order and remove the dummy unit & therefor the aura buff.
I've attatched a photo i've what i've tried, but it doesn't work (i know why).
what i dont know is how to make it work.

If anyone out there has dealt with this problem or something similar, any information would be very useful. Thank You! =D

hosted @ image shack

 

[nabbig2]

Maybe you could assign the dummy to a variable first-
Then, in the event Unit Stops Casting An Ability=Your Ability
Then destroy the dummy.

 

[SerraAvenger]

Well, can there be multiple of this thorns aura casting units per player, or just one per player?

 

[Griffen25]

Maybe you could assign the dummy to a variable first-
Then, in the event Unit Stops Casting An Ability=Your Ability
Then destroy the dummy.

Thank you that helped alot, I've also learnt an important lesson about variables and there potential. Truly, Thanks!
+rep