Xslt debugger tools dealing with <msxsl:script>

Does anyone know Xslt debugger tool that can recognize and debugge the
<msxsl:script> element and the embedded script inside it?

I used some debuggers like XMLSPY, but it consider a call to function
defined in embedded script like "<xsl:value-of
select='UDF:SomeFunction();'/>", it consider it as a not valid XPath
or variable.

I already know that <msxsl:script> element is Microsoft extension to
Xslt standards so its not expected to find alot -if not at all- of
debuggers dealing with such element, but maybe someone can guide me
here.

Thanx in advance.