John,
Normally the way I handle this is that in your user table, you set up a USERLEVEL field (minimally with a Normal user designation and a Special user designation). Then if it's a Special user, add a menu item that allows access to the Add User form. (Or you can start with it in the menu, and remove it if it isn't a Special user. Or you can use a Skip For clause in the Menu, so it's just disabled for non-Special users. You can pick which method is appropriate, depending on what you and/or your users think is "right".)
Rick