Selective moderator assignment

How can setup a system such that a group of users can have its separate moderator user who is able to edit their profiles?

CB isn't really setup for this. I recall helping someone accomplish something like this awhile back using an odd combination of actions in CB Auto Actions, but you'll need to search for said post. You basically have to have a read only field for the user that stores the user_id of the moderator. You'd then redirect from profile edit if the user trying to edit isn't the profile owner or isn't the moderator.

pls give me some clues for keywords....

I don't have any, sorry. I've briefly explained how in my previous post.

i guess u are referring to this link: www.joomlapolis.com/forum/154-advanced-members-support/192439-assign-specific-moderator#192514

Please clear one aspect:
If I am logged in as the moderator user then setting the User in auto action to Automatic, I can access the moderatorid field of the other user whose profile I am viewing. Now [user_id] will give me the userid of the other user whose profile I am viewing so how do I access the userid of the moderator profile from which I am logged in?

You'd want to ensure first that the users who will be editing other users are CB Moderators. Lets for examples sake say their usergroup is "Author". Now you'd create a CB Auto Actions "Redirect" action. You'd then probably use the trigger onBeforeUserProfileEditDisplay. Next ensure the access is set to "Author". Once done add conditions to check that the moderator field where the moderator user id does not match the viewing users user id and redirect away, example as follows.

[cb_mymod] Not Equal To [cb:userdata field="user_id" user="#me" /]