Is there a way to add temporary hit points on conditional damage?

I'm creating a sort of like, underworld cleric class i guess. It's a lot of necrotic damage, sustain and frightening, at least that's my idea for the class.

I have an idea for an 6th level ability.

Whenever you deal necrotic damage with a spell or Channel Divinity: Damnation, you regain hit points equal to your wisdom modifier (minimum 1), up to max health if possible. If the target is frightened, cursed, or restrained, you regain double that amount. This can only trigger once per turn.

Since it's conditional, is this actually able to be added to a class? or is it just too complicated.
Any help is greatly appreciated.