Xsl on IIS with integrated windows authentication enab

I am using Saxon B 8.4 and IIS 5 with Integrated Windows Authentication
enabled. My question is how do I pass the current user credentials to
the transformer so that my document() functions work with an asp.net
program that returns xml?

The transformation works fine when I test the xsl on an site with
anonymous access enabled.

Document example:
	document('http://site/priority.aspx')

Any ideas?

Thanks
Jeremy