msxsl:node-set() not recognized - xslt

Question

I am trying to pull nodes out of a node set stored in a variable using the msxsl:node-set() function and am not getting anything. My xml looks like this:
<Root>
<Items olditemnumber="100" newitemnumber="200">
<Item ItemNumber="100" ItemAliasCode="1001" ItemCode="X" />
<Item ItemNumber="100" ItemAliasCode="1002" ItemCode="X" />
<Item ItemNumber="200" ItemAliasCode="2001" ItemCode="X" />
<Item ItemNumber="200" ItemAliasCode="2003" ItemCode="X" />
<Item ItemNumber="100" ItemAliasCode="1003" ItemCode="P" />
<Item ItemNumber="100" ItemAliasCode="1004" ItemCode="P" />
<Item ItemNumber="200" ItemAliasCode="2002" ItemCode="P" />
</Items>
</Root>
In my xslt I try to populate a variable with a subset of the nodes and then call them using the msxsl:node-set() function. This doesn't return anything however.
XSLT looks like this:
<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:msxsl="urn:schemas-microsoft-com:xslt">
<xsl:template match="//Root">
<xsl:variable name="OldItemNumber" select="/Items/#olditemnumber"/>
<xsl:variable name="NewItemNumber" select="/Items/#newitemnumber"/>
<xsl:variable name="OldItems">
<xsl:value-of select="//Item[#ItemNumber = $OldItemNumber]"/>
</xsl:variable>
<xsl:variable name="NewItems">
<xsl:value-of select="//Item[#ItemNumber = $NewItemNumber]"/>
</xsl:variable>
<xsl:for-each select="msxsl:node-set($OldItems)/Item">
...work
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
The XSLT skips over the for-each loop, though I see in the watch that the the Xpath query grabs the right nodes in assigning the variables. The watch also tells me that the msxsl:node-set() function is undefined. Any help would be appreciated. What am I missing?

Answer 1

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:msxsl="urn:schemas-microsoft-com:xslt">
<xsl:template match="//Root">
<xsl:variable name="OldItemNumber" select="/Items/#olditemnumber"/>
<xsl:variable name="NewItemNumber" select="/Items/#newitemnumber"/>
<xsl:variable name="OldItems" select="//Item[#ItemNumber = $OldItemNumber]"/>
<xsl:variable name="NewItems" select="//Item[#ItemNumber = $NewItemNumber]"/>
<xsl:for-each select="$OldItems">
...work
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
msxsl:node-set is for converting a result tree fragment (a.k.a. RTF) to a node set, which is not needed on your case.
xsl:value-of is for creating text nodes, so don't use it for selecting nodes of the input tree that you want to further query/process.