Phoenix Fire costing mana...

How do I make it so that with every volley fired, it saps mana? I set the mana cost to an amount but it doesn't deduct the mana. Is there any way to do so? (without triggering, since phoenix fire has no order code)

Just do a trigger if unit is alive and has the ability... reduce mana each second.

Oh yea, every .85 seconds reduce it by X amount. That works. Hadn't thought of that one...