SETFable join slots?

One thing I'd like to do with CLSQL is:

  (push *bob* (account-customers *yoyodne-inc*))

where ACCOUNT-CUSTOMERS is a join slot.  Then when
UPDATE-RECORDS-FROM-INSTANCE is called on *BOB*, I'd like *BOB*'s
account-id field to be set to the id of *YOYODYNE-INC* (or whatever
the right thing would be, based on the join-info).  It doesn't seem
that CLSQL supports this now - are there subtle, hard-to-get-right
issues with this, or is it just that no one has added this support
yet?  If the latter is the case, I plan to add support for this within
the next couple of weeks.  If CLSQL already supports this, please let
me know and disregard this message. :)

--
Bill Atkins