[Zope] filtering results

[gf]

Hi,
I am a Zope newbie. I apologize if the terminology I use below is not
correct, but I hope that you get the gist of what I am about to ask.

I would like to be able to 'filter' results before returning them to
the user.  In other words, if a user requests a given object, it is
passed through a filter before being passed on to him or her. As a
simple example, I may want to tidy the html before the user sees it,
or eliminate or add certain tags or words.

I have put together a simple 'html tidy' external method that takes
raw html and produces a tidied version, but I don't know how I can
apply it.

Thank you for any comments, suggestions, or simple examples you may be
able to provide.

Best  Regards,
gyro