Spells, yes. Weapon attacks, I don't think so.
If you're talking about spells, just create a magic effect with Script effect archetype. Then use the script to deal damage.
EDIT: If you don't want to use scripting and DamageAV("Health") to actually deal the damage, then you could instead create a spell with many copies of the same magic effect. Each copy would have slightly differing magnitudes/durations. Make the effects conditional on a value you can set somewhere, like in a script using RandomInt.