Only allow a trigger once per "fight"

[Darkark]

Is there a way to prevent a trigger from reoccurring during a single fight? One example might be: NPC begins to cast <Spell 1> (Phase 1 has started), followed by many casts of <Spell 1>, until NPC begins to cast <Spell 2> (Phase 2 has started), followed by many casts of <Spell 2>, etc.

Basically, I don't care that the NPC has cast this spell each time, I only care about it happening the first time.

Thanks!

[Sirene]

One way you could do this is to make a count up timer: