lo_unlink from a trigger

I'm using large objects, and storing the OID of the object in a table.
What I'd like to do is to clean up the object automatically when the
corresponding row is deleted, via a trigger or rule.  Are there any hints
on how to do this?  Can it only be done via an external language (such as
C), or is there a way to do this in native pl/psql?

--
Jeff Boes                                      vox 616.226.9550 ext 24
Database Engineer                                     fax 616.349.9076
Nexcerpt, Inc.                                 http://www.nexcerpt.com
           ...Nexcerpt... Extend your Expertise