[Zope] Raise Unauthorized?! - and logging in new users: two questions

Hi Zopers, I did some research on this ... but im up against deadlines :-) (1): Apparently <dtml-raise Unauthorized> creates a "rendering loop". That is, you raise Unauthorized, get the login screen, enter a VALID userid/password, click OK and you get yet ANOTHER login screen. This isnt very helpful. I want to be able to login new users without the need for the user to terminate the browser and restart. I am really hoping that someone has solved this problem (without turning to 3rd party login managers). (2): Also, is there a way to login a user "programmically", that is, by avoiding the browser login screen and logging the user in via a python script or DTML???? Any insights please! Thanks, David