Templates, variables, and tree fragments

I have a XSLT document that is correctly transforming the data, but I need
to use the output of that transformation to build some of the nodes I need.
I'd like to find a way to do this in one XSLT document, and not have to run
two back to back transformations.

The below is a cut down version of the problem.  The template for
KH/Key/MD/@AskAvl can change the value in the attribute.  The output of the
'row' node produced in the transform ion (RowMD template) shows the starting
XML value of @AskAvl.  But, I need the @AskAvl that was produced in the
rebuilt 'MD' node (KH/Key/MD template)

<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform" >
	<xsl:output method="html"/>
	<xsl:template match="*">
		<xsl:copy>
			<xsl:copy-of select="@*"/>
			<xsl:apply-templates select="node()"/>
		</xsl:copy>
	</xsl:template>

	<xsl:template match="KH/Key/MD" priority="999999">
		<xsl:element name="MD">
			<xsl:apply-templates select="@*"/>
			<xsl:call-template name="RowMD"/>
		</xsl:element>
	</xsl:template>

	<xsl:template match="KH/Key/MD/@AskAvl" priority="999999">
		<xsl:attribute name="AskAvl"> NEW </xsl:attribute>
	</xsl:template>

	<xsl:template match="@*">
		<xsl:copy-of select="."/>
	</xsl:template>

	<xsl:template name="RowMD">
		<xsl:variable name="Market" select="current()"/>
		<xsl:element name="row">
			<xsl:attribute name="data">
				<xsl:value-of select="$Market/@AskAvl"/>
			</xsl:attribute>
		</xsl:element>
	</xsl:template>

I read a snippet somewhere (don't remember where I saw it) that indicated
variables could call templates, so I tried -
	<xsl:template name="RowMD">
		<xsl:variable name="Market">
			<xsl:element name="MD">
				<xsl:apply-templates select="@*"/>
			</xsl:element>
		</xsl:variable >

(When RowMD is called the current node is an MD node.)  This produces an
error stating that the market variable does not have a nodeset.
But, when I changes it to -
	<xsl:template name="RowMD">
		<xsl:variable name="AskAvl">
			<xsl:apply-templates select="@AskAvl"/>
		</xsl:variable >
		<xsl:element name="row">
			<xsl:attribute name="data">
				<xsl:value-of select="$AskAvl"/>
			</xsl:attribute>
		</xsl:element>
This appears to work, I get the value 'NEW' in the row node data attribute
and in the AskAvl attribute in the MD node.  But, I'd like to understand why
the creation of the MD element did not work.


Sample XML -
<QuoteData>
<Data>
<Map schema="7" col0="12" col1="2" col2="2" col3="2" col4="2" col5="2" >
</Data>
<Data>
<KH KHID="415" Type="401" QSID="5">
<Key KeyID="5505">
<MD Dep="1" BidCPID="177" BidAvl="1"  AskAvl="44" AskCPID="8" />
<MD Dep="2" BidCPID="177" BidAvl=""  AskAvl="3" AskCPID="8" />
</Key>
<Key KeyID="552">
<MD Dep="1" BidCPID="1" BidAvl=""  AskAvl="5" AskCPID="177" />
</Key>
</KH>
</Data>
</QuoteData>



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