I'm using a modified portcullis changed to look like a section of wall.
It has the Default2StateActivator script.

I put a trigger box around it and will set it as the Activate Parent of the portcullis.
I'm thinking I could use the DefaultActivateSelf script from the Warehouse Ambushes with OnTriggerEnter changed to OnTriggerLeave and most of the part about followers and activation by others removed.
But how will I tell it to only activate if the portcullis is already open?

If I cut away what I think isn't needed it looks like this:

ScriptName CloseDoor extends objectReference
{script that simply activates itself when player leaves trigger}

import game
import debug

bool property doOnce = FALSE auto
{Fire only once? Default: FALSE}
bool property disableWhenDone = FALSE auto
{Disable after activating? Default: FALSE}
bool property playerOnly = TRUE auto
{Only Player Triggers? Default: TRUE}

;************************************
auto State waiting

Event onTriggerLeave(objectReference triggerRef)
Actor actorRef = triggerRef as Actor
if(actorRef == game.getPlayer()); check whether the player is activating

if(PORTCULLIS IS OPEN)

if doOnce == TRUE
gotoState("allDone")
endif

if disableWhenDone
Self.Disable()
endIf

activate(self); pass self as the activating ref

endif
endif

endEvent

endState

;************************************

This will tell you what state the door is in.

http://www.creationkit.com/GetOpenState_-_ObjectReference


And its probably better to use this to open or close the door:

http://www.creationkit.com/SetOpen_-_ObjectReference

I tried your suggestion. The lines with semicolons failed to compile either singly or together. The "door" it's refering to isn't really a door but a section of wall that slides up. It's listed as an activator not a door. Does that make a difference?

Scriptname CloseDoorScript Extends ObjectReference

Activator Property MyDoor Auto
Actor Property PlayerREF Auto
Int Property OpenState Auto

Event OnTriggerLeave(ObjectReference akActionRef)

;OpenState = MyDoor.GetOpenState()

If akActionRef == PlayerREF
;If (OpenState == 1 || OpenState == 2)
;MyDoor.SetOpen(false)
;EndIf
EndIf
Debug.Messagebox("yipee")
EndEvent

Only a 'door' object can use SetOpen and OpenState. Since you are using an 'activator' object, you cannot use these door commands.

So that means you have to remember what state the activator is in, using a variable. I would recommend this triggerzone is the only way to open it as well.
So, open on enter and close on leave.

"So that means you have to remember what state the activator is in, using a variable. I would recommend this triggerzone is the only way to open it as well.
So, open on enter and close on leave."

+1 - There are several Dwemer traps that use this method (eg spinning blades) that can be found in the 'warehouse traps' if you need a closer look.

Having the triggerbox only to open or close it wouldn't work. I was trying to get a secret door that you open manually with a semi- hidden pull chain but that closed automatically when you moved away from it.
Second choice would be having the portcullis always start closed when you entered the cell somehow.
I was looking over the Default2StateActivator script on the portcullis but I really don't what all the Events and Functions mean. The script takes 3 pages

Solved it finally.
I added these lines to the Default2stateactivator script.

objectreference property mypullchain1 auto
objectreference property mypullchain2 auto


auto STATE waiting ; waiting to be activated
EVENT onActivate (objectReference triggerRef)
if (isOpen || (triggerRef == mypullchain1) || (triggerRef == mypullchain2))
; Debug.Trace("d2SA RESETS: " + Self + " " + isOpen)
; switch open state when activated
SetOpen(!isOpen)
if (doOnce)
gotostate("done")
endif
endif
endEVENT
endState