HOW TO MANAGE USER RÔLE ?

Hi, 

Here is the context. Client has 3 levels of division in the CRM : Level 1 for the all group, Level2 for region and level 3 for the store.

Needs : We need to allow users to see only opportunities about their store. But if they open a contact, the must be abble to see all opportunities attached to the contact.

How can we deal with?

Sincererly yours;