[Zope] about restricting addable types in Plone

[Sergio Gomez]

Hi all,
I am working with Plone 2.1.2, Zope 2.8.6 and python 2.3.5. I would
like to know if there is a way to restrict addable types to a
folderish object programmatically.
What I need is to allow adding a certain type of items and not otheres
depending on the value of one field in my folderish object.
For example, if the value of the field is "0", I can only add "News
Item", if the value is "1", I can only add "File", and so on.

Thanks!
Sergio