[Zope] delete dictionary

[urs.beyeler]

hello,
i've created some dictionaries in a dtml-document, for example like this:

<dtml-call "REQUEST.set('Monday',{'titel' : 'this is to do on monday'})">
<dtml-call "REQUEST.set('Tuesday',{'titel' : 'this is very bizarrr'})">
<dtml-call "REQUEST.set('Wednesday',{'titel' : 'how to do that?'})">

... and a bit later in the document i need to delete them again ... 
how can i do that? no one of my DELETE-experiments worked ... thnx.urs