I have a client that wants to use sugarcrm to manage client data.

The clients users / data falls across multiple countries and thier regions.
There are users required to manage the region
with the region there are user that need to manage spasific groups of clients,and none other..
there also need to be uses say dedicated to marketing and not have access to client data but still fall into the country - region - group tree ...

How could this be done ...

Note client privace is top priority, if a user is not assigned to see a user or group, then there must be no way for them to acces it ..

Many thanks..