How to retrieve Org.Units within Organization units

Hello,

Im working with version SRM 5.5.

For a report - Zeta - I need to find the users within an org.unit and also the user within the subordinate org.units.

From these user I need to show information of the their Shopping carts.

What FM helps me to find:

1. Users within an Org.Unit

2. Org.units within (hierarchically) the Organization unit.

Or is it the same FM.

thanks for any reply.

Aart