Grant access when node referenced changed

This is the situation:

A region content type with userreference "Administrators"
A country content type with nodereference "Region"
A product content type with nodereference "Country"

Nodeaccess module allow to grant view/update/delete access to user referenced in "Administrators" field. This is ok.
I give pass update in "Region" Nodereference in Country for users that can update Region. This is ok for existing users that can update Region, but if I change Region administrators, Region access change, but not Country.

Example:

Country "Argentina" is referencing to Region "South America". This region have a referenced user "admin a", this user can now edit "South America" and "Argentina" nodes. Adding new user to "South America", "admin b", this user (and "admin a) can now Edit "South America", but "admin b" cannot edit "Argentina"

my aplogize for my english, this is my best try.