[support] Secondary registration

[Roger]

Hi
  I hope someone can help.
On one of our sites, the viewer can create an account and be redirected 
to the event registration page.

However we need to differentiate between members and the public and I 
can find no way to provide a validation procedure that allows members 
who have created their account to enter a validation code only known by 
members so they can be redirected elsewhere.

Is there a module that can handle something like this scenario, if not 
how could I do this secondary login?
thanks in advance
Roger