Help: AOE Protect spell?

Help: AOE Protect spell?

I'm trying to make an AOE protect spell that adds a buff to friendly units within the aoe that reduces damage by a certain %, but I can't seem to get it to work.

Any ideas on a good way to go about doing this?

Thanks in advance.

Just make a common pick-unit function and let a dummy cast Cripple on the targets.

.... or create dummy units on the center of AOE, order it to cast howl of terror.

Thanks. I was trying to do it in JASS but I kept breaking it.