How do I make a unit cast a spell instantly?

I dont want any casting animation, no casting time, just when i order the unit to cast that spell he casts it within a split second.

EDIT: I tried putting casting time to 0.00, wont work.

i think u can't, really...

Casting Backswing Point - change it to 0 on the unit.

that works ? tnx man....i didn't know that :)