[Zope] Create or edit instance objects

[Pablo Ziliani]

Dear Zopeists:

I guess my problem should be a classical one, but I still havenīt found a 
solution in any How-to or message in this list, so I have no choice to ask 
for your help.

- HELP!!!!
  How can I make the same method that creates an instance object
  to edit it?

Note: - my class uses Propertysheets
      - my class uses random ids.
      - I would like to avoid to create the instance object
        before all the data is set in the REQUEST (and the
        button "create" has been clicked) so no garbage is
        to be later cleaned.

Lots of thanks in advance,
PABLO.