[Zope] uniqueValuesFor from only part of the catalog?

[Jonathan Cheyne]

How can I prefilter the catalog so that the list of unique values only
comes from records containing a specific keyword?

I set up a keywords index as per one of the howtos whic works well and I
can extract a unique values list with 

<dtml-in "Catalog.uniqueValuesFor('keywords')">

but I only want to see part of the catalog ... how?


(this is a follow up to my earlier rather rambling plea :-)

Jonathan