What's the trick to doing parenthetical-like queries with FindPagesByCriteria?  In my case, I need pages from one of two categories that also match one of two page types.

In fake SQL terms, I need something like this:

WHERE
    (cat_id = 1 OR cat_id = 2)
        AND
    (page_type = "Text Page" OR page_type = "News Article")

I can't figure out how to do this by juggling the "Required" property on the PropertyCriteria object.  What I need is two different PropertyCriteriaCollections -- one for the category and one for the page type.  The criteria in each would be required=false (because it could be one category OR the other), but between the two collections, they both have to evaluate to true.

It's weird, I know.  Any way to do this?