Start a quest with dialogue?

[TotallyExoticHD]

I'm trying to get a quest to start when the player tells the NPC that they can go visit a vault that the NPC is from.

 

I want the new quest to start when the dialogue finishes with the NPC, I have tried this but the quest doesn't work, it just goes to the next phase of dialogue even though that part of the phase isn't linked, it's supposed to end the running scene.

 

I've done this :

 

 

Anyone know how to do it? Thanks.

 

EDIT:

ChristopherVaultQuest is the quest I want to start.