[Zope] prevent user aquisition with custom userfolder

[zope-mailinglist]

hello all

some problem with user and access stuff:

iv'e written my own user and userfolder classes which work just fine, 
but i need a special behaviour:

if a userfolder is defined in an objectmanger instance only those users 
defined in this specific userfolder should be valid in the context.
the normal behaviour -- as you might now -- is to inherit the users from 
the parents

it seems that this can not be done in the userfolder itself -- of course

somewhere in the zope machinery ther must be some aq_parent stuff when 
authorizing a user to a specific context

has anybody got an idea where i can subclass something and override the 
dependent methods?

thanks in advance, bernd