Hide guests from agents

It will be grait to assign agent to special organization and disable view and serch other guests, organizations. or do this thing with groups or departments.

I mean agent can view only his group.

Now i used to add this by php, by adding <?php if($thisstaff->isAdmin() && !defined('ADMINPAGE')) and fully hide guest or for example ability to add new user or organisation {?> or making if $thisstaff->getUsername() == xxxx;