> I can create the function the trigger is calling, and I can use the function
> in a SELECT, and it all works fine, but postgres won't let me create a
> trigger using that function.
Follow the below link to learn howto write triggered procedures:
http://www.postgresql.org/docs/view.php?version=7.3&idoc=1&file=plpgsql-trigger.html
regards,
bhuvaneswaran