[Zope] Switching users with loginmanager

[Sergio Fogel]

I am having difficulties switching users with loginmanager. I have an entry
page, which is lnked from an external site. The other site sets __ac_user
and __ac_password before linking (through a form with method=POST). If my
user follows the link, he can access the page without problems. The problem
is that if he changes user in the external site and follows the link again,
__ac_user is ignored, since the user is already authenticated, and from the
Zope point of view it is still the same old user. Any clues about how to
force re-authentication in that page? By the way, redirect will not work
because I need some other fields in the POST, and I would not want them to
be shown in the URL.

Thanks,

Sergio