[Zope-CMF] Paying Portals & Progress

[BZ]

I am working on a CMF portal that requires members to pay before 
accessing the site <gasp!>. I am using PayPal to do the payment 
processing but am hitting up against the process flow of registration 
in that it actually creates the user folder as the first step after 
"login_form".

Has anyone figured a good way of doing this? Here is what I have come 
up with (untested).

1) login_form
2) register (created user folder, sets active= to unchecked)
3) Feed PayPal with information (as much as they will take)
4) At end of PayPal there is a "return_url"  which I set with the 
memberID and another parameter that when they come back sets the 
active=Y.
5) Chenge login to now allow someone to log in if the active for the 
account is not set.

Obviously if you know the way to pass the parameters back you can 
foil the system but I am willing to do some sort of manual 
intervention as I will keep books offline.

The only other way I can think of is to set a cookie on the user and 
check that when they come back from PayPal.

So... am I way off base here?

Thanks,
BZ