[Zope] Dtml-with & Session

Hi all Hope someone can help me with this. I first start a session called seesion with a var called placetostore I then call my session var from another page like this. <dtml-with session> <dtml-let a=getSessionData> <dtml-let x="a.get('placetostore')"> <dtml-var x> </dtml-let> </dtml-with> This works fine I cet the var I was looking for. Now If I try to do <dtml-with x> <dtml-call "REQUEST.set('ArtNo',REQUEST.form['new_ArtNo'])"> etc etc etc. Every time I get the page It get a http auth box. now I don´t have a clue why. How should I call this var x I just created? Any tips/hint are welcome! :-) thanx and Greetz, James van der veen