Hi Mark,
Here is how I used it
http://cvs.openacs.org/cvs/~checkout~/openacs-4/contrib/packages/bcms/tcl/bcms-item-procs.tcl?rev=1.1&content-type=text/plain
look at list_related_items, relate_item and unrelate_item
This still needs a lot of work, after my current project hopefully I can start working on it again.