How to I catch the referring OrgUnit (from the tree)?

Hi,

What the OrgUnit list shows
http://dhis.uio.no/demo/dhis-web-maintenance-organisationunit/organisationUnit.action

depends on what has which parent orgunit has been clicked on in the
orgunit tree on the left.

How can I capture this parentid for use in javascript on the list
page? I can easily get the id for each of the subunits in the list,
but how about the parent?

Knut