need to make a guard tower attack more than one person

need to make a guard tower attack more than one person

I need to make a guard tower to attack 4 people at the same time. i have tried a lot of triggers but none of them seem to work. help please!!

Make a new custom ability out of Barrage, change the targets to enemy, ground, air, put the number of missles to four, change the radius/distance to same range as tower, and set all of the damages to 0.

Thanks, i worked good