Hide Specific UserGroup from Control Panel

[hurrican]

Isn't there some way to hide a specific UserGroupID in the CP from being selected using a mysql != statement somewhere in the admin/user.php file? I want to have UserGroupID 15 NOT available to a choice, but don't want to remove that particular group from my forum (it's used for external suspensions).

If easier, I'd be happy with if another admin were to select that usergroup to change a user to, that when they clicked "Submit" it would error out on them telling them that the UserGroup chosen is not available, to use the external script written for that usergroup. Any help greatly appreciated.