I spent quite some time searching here for some sample code/db where a treeview populates from a table, because several posts indicated there had been posts on this, but I couldn't find anything. So I then went back and STFW and found something that looks pretty good at

http://www.access-programmers.co.uk/forums/showthread.php?t=98659

Reposting here for posterity.

Maybe my delicious bookmarks on this topic could also be helpful:

http://del.icio.us/tphyahoo/tree

UPDATE: See also

http://www.access-programmers.co.uk/forums/showthread.php?t=80805&highlight=treeview

at this forum, which has another example.