How to implement typical security rule to user group?

I am implementing security rules in openERP for CRM.
Now I want to restrict user group to update certain values.
Now sale person can qualify opportunity but can not "mark won"
Sales manager only can do "mark won".
How can I implement this in openerp? Does this possible !!! OpenERP 7.0 Stable
Now I want to restrict user group to update certain values.
Now sale person can qualify opportunity but can not "mark won"
Sales manager only can do "mark won".
How can I implement this in openerp? Does this possible !!! OpenERP 7.0 Stable