Well i tried some configurations with joomla acl and seblod. And I figure out how to do this.
It's very simple to do this.
1 - In menu joomla users groups create two groups "group a" and "group b". This groups needs to be child of group "manager".
2 - In menu access levels create two access levels "access level a" and "access level b".
3 - Assign the "group a" to "access level a" and "group b" to "access level b".
4 - Create the users, and do the same thing. Assign "User a" to "group a", and "User b" to "group b".
5 - Create your fields normally and choose the button 4 (Access + Restriction).
6 - In seblod your fields come with value "public" by default. When your field is public, all users be able to see this field. Now you just have to change the access level that you want to able to see the field.
Result:
If access level is "access level a", just users is assigned to this access can see this field.
If access level is "access level b", just users is assigned to this access can see this field.
If access level is "public", all users can see this field.
Thanks to all!