Make zoning-permission for creating childzones

I would like this to work in WorldGuard:

Admin defines an area called city1 and adds Player1 as owner.
Admin defines an area called city2 and ands Player2 as owner.

Player1 may now create childzones and addmember/owner to childzones in city1.
Player1 may NOT create zones or addmembers/owners in city2.
Player1 may NOT create zones outside city1.

Please, implement this. :D
