ROTEL'S PROFILE

I have looked around quite a lot and can't seem to find an answer to this, but I am trying to make an NPC have three different lines of dialogue, however only one is used at a time and in a specific order. So:

Player interacts with NPC, NPC says dialogue #1, end event. Player interacts with NPC, NPC says dialogue #2, end event. Player interacts with NPC, NPC says dialogue #3, end event.

I know I can make it so the dialogue just comes all at once, but I want it broken up so player can approach NPC more than once.

I was thinking it would need some kind of variable? I'm having trouble figuring it out or finding it anywhere else on the web.