gen_event question

[David Best]

I have a process A which maintains some state and also fires events
(generally state change notifications) using a gen_event process V.

Enter process B which needs to atomically get the current state of A
and add a handler to V.  This is easily done by including B's event
handler in a message to A which will add the handler and pass the
state in the Handler:init/1 Args.

The complication is that I want to use add_sup_handler/3, but this
will link to A instead of B.

Any suggestions?