Trigger for visited area?

Say I have a creature that can teleport me to various area through dialogue actions, but I only want the response for each travel option to be available only if the area has been visited before.

Is there a trigger - like VisitedArea("AreaRes") - to allow this? Or do I have to EXTEND_TOP every one of those areas with some

IF
	OnCreation()
	Global("VisitedThisArea","GLOBAL",0)
THEN
	RESPONSE #100
		SetGlobal("Visited[Area]","GLOBAL"1)

and check for Global("Visited[Area]","GLOBAL",1) in each response?