asterisk users - Jul 2007 - Parking calls via cli / manager / dialplan

I would like to build into our application a button to "park" and a 
button to "unpark" calls.

Consider this scenario:

Agent A gets a call, and obtains a reference number. He needs to send 
this client to another Agent.

Agent A pushes the "park" button. The call is then parked into a 
designated slot based on the reference number . Agent A then calls Agent 
B and tells him that there is a call for him, and gives him the reference. 

Agent B enters the reference and then pushes a button to retrieve the call .

What I think I need from this is the facility to specify a slot to park 
the call in, and the slot to retrieve from.

Is this possible with 1.4 ?

Julian