Hit another dead end

Alright ive hit another problem and im curious if anybody know how to fix it. Anyway the problem is that I have a text event for a trigger, and the condition is that the player is (riddled player). Although this is good for the actual condition (they must go through the starting quest trigger) I don't know how to unset the variable afterwards! Which means after they activate the first trigger they can say the activating event over and over and reactivate the trigger! And considering the trigger has a reward they could use this as an exploit. Does anybody know any way to unset a variable after it is set?

edit: let me be more specific

First trigger:
Event: unit- a unit enters Riddle<gen>

Conditions: (triggering unit is a hero) equal to true

actions: Set RiddledPlayer = (Owner oif (Triggering unit))

then the rest of the actions.


Second trigger:
Event: Bla bla bla player says "tree" as an exact match

Conditions: ((Triggering player) Equal to RiddledPlayer)

This is where I get stuck

Yes, go to the trigger where you made the reward and the very last thnig make an action called Set Variable. Then just change your variable to something else, shouldn't matter what you change it too, as long as it isnt the same as what it was for the trigger to activate.

Alright thanks. I changed the setting to player green which is a computer :D

Trigger - Turn off this trigger