Making Spells Auto-cast?

Just curious, but is there a way to make spells auto-cast like Animate Dead? :(

I believe you have to base it off a spell that auto casts. For animate , lets say that you want it to go off when you attack a a unit. You would base it off of lust, then give it the attributes of Animate . If you wanted it to go off when you were attacked, you would have to base it off of something like frost armor. I'm pretty sure the auto-cast's are hard-coded into your base spell.

First create a dummy unit ( a unit that is invisible and unselectable, and invulnerable, it also has no model), then, create a dummy spell that does based on an auto-cast spell, then, make your real spell, use this trigger:
Events - A unit starts the effect off an abillity
Conditions - Abillity beign cast equal to (the dummy spell)
Actions - Create 1 (Dummy Unit) for owner of casting unit at position of casting unit
Unit - add expiration timmer 1.00 seconds to last created unit(may be longer depend of the spell that you wish to cast)
Unit - Add (the real spell) to last created unit
Unit - Issue order to last created unit -(your spell order) on target unit of abillity beign cast.