You're doing it wrong, way wrong.
What you gotta do is create an alias for your door in your quest and create & attach a script to it that has an OnOpen event.
Put this in your door's ReferenceAlias script:
event OnOpen(ObjectReference akActionRef)if(GetOwningQuest().GetStage() == 10) GetOwningQuest().SetStage(20)endifendevent
Put any other scripting stuff you need inside the stage you just set to.
Everything should work this way. Remember, aliases are your best friends.
