I would like to use the private registration but we require on additional piece of information unique to our organization (a national membership number).  Is there a way to add a field to the registration page used by the private security setting? 

Sorry I was not clear.  There is a Private registration setting so that a user can registrer and the registration is sent to the webmaster for approval.  The approval must be done before the new user can logon the site. 

When you turn on the Private registriation and the user clicks on Register, he can only enter basic information like User Name, first/last name, password and e-mail.  The problem I have is that I require one additional piece of information (in this case a national membership number) that I need to verify before I can approve the new user.  So, I am looking for a way to add one additional required field to the Register dialog.