>>>>> "Bruce" == Bruce D'Arcus <bdarcus@xxxxxxxxxxxxx> writes:

    Bruce> So what I want to do is is define an output-format
    Bruce> parameter in my main stylesheet (as above).

Perhaps you could get the effect you want by an auxiliary document.
The fn:doc function (but NOT the document function) is in scope for
use-when, so you could contruct an XPath expression which tested the
value of an attribute within the auxiliary document.
-- 
Colin Paul Adams
Preston Lancashire