[O] Refile: refile to any open file.

[lngndvs]

It  occurs from time to time that I wish to refile to an open file, that
is not one of my org-refile-targets.  It doesn't make sense to use
org-agenda-files for refile targets since I might have other files open
for various reasons.  So I thought, why not either declare that any open
file is a refile target, or else write a function that will execture
org-refile with org-refile-targets set to include all open files.   In
truth, it would be even better to include org-agenda-files in the set of
target files.   

I have been using the function oog in org-occur-goto.el to search any
open file, so somewhere in that file is a way to find  open files.  What
remains is to use some condition from this file to declare
org-refile-targets.   I understand that a function can be used as a
value of this variable.  

I could spend all night working on this, or, ask on this list.

Can anyone point to a good way to declare that BOTH all open
buffers/files AND org-agenda-files as org-refile-targets?

A hint would help.

Alan Davis