[Zope] setCookie

I want to set a cookie with the username of the visitor of my site using: <dtml-call "REQUEST.setCookie('username', '<dtml-var unaam>')"> but it doesn't set the cookie. I've tried several things and i've read the zope book pdf file and done it like it says in the book but it still doesn't work. The cookie exists i checked that with <dtml-if username> but when i try <dtml-var username> it doesn't display the username. How do i set the cookie in dtml or python and how do I get the data out of the cookie? thanks, Sebastiaan Schimmel sebastiaan_schimmel@planet.nl