[Zope] Change form data in request

[Paolo Dina]

Hi all.

I know that the request object stores all the informations about the 
current request, i.e. cookies, server data, form data and input headers.

So, i get request using this syntax:
r = context.request
And using .set it is possible to change values of variables stored in 
request.
Now the question: why

r.set( 'name', 'newvalue' ) # changes a variable in 'option' section 
of request
works, and

r.set( r.form[ 'variable_in_form' ], 'newvalue' )
does not?

I need to modify a variable stored in 'form'!
Any hints?

Thanks
Paolo Dina

P.S.
An other guy had the same problem 
(http://mail.zope.org/pipermail/zope/2000-August/116799.html), but no 
solution was emerged :\