[Evolution] Searching Contacts

[Paul Hands <phands cadence com>]

I'd like to search my contacts database for a field and value which are
not in the standard searches.  For instance, I'd like to be able to pick
cards which have a Category called Organization, and a given value, say
CAD.
I guess it might be in the advanced search section, and maybe something
to do with expressions.  What eludes me right now is what is an
expression in this context?  The help doesn't seem to mention it, and,
as far I can see, it's not covered in the mailing list archive or the
FAQ.

Thanks,

Paul