Help needed to setup special editing permissions for a user

[Sicilian]

If I set time limit on editing posts to '0', it will mean that all registered users will be able to edit their posts indefinitely. I've set this to 30mins so normal registered users have a chance to edit their posts.

Now if I give this user Moderator class, then the user would have access to edit/delete anything thread/post on the forums.

I just want to set one particular usergroup to be able to edit/delete/close their own threads without giving them Moderator class.