Debugging XSL with XML Spy 5

Does anybody know anything about the internal xsl processor that ships with
XML Spy 5 ?
This is the processor that Spy uses when with its debugging tool.
The problem I have is that my transforms use an extension function - namely
msxml's node-set function. Does anybody know if there is an equivalent in
Spy's processor and if so what the namespace is.

Thanks

Dave

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