How to create epilogue triggers?

Looking for technical advice: I want to create a new variable that is attached to a specific line of dialogue; if this line is selected by the player, it will trigger an alternate epilogue for a specific party member at the end of ToB. How would I go about doing this?

EDIT: Also, is there a way to attach a similar variable to a character's class? (ie: they get one epilogue if they're a paladin and one if they're a fallen paladin)