Referencing value of non-sibling node

Sample Input File segment:
<md>
...
	<mi>
...
		<mt>mtVal1</mt>
		<mt>mtVal2</mt>
		<mt>mtVal3</mt>
		<mt>mtVal4</mt>
		<mt>mtVal4</mt>
		<mv>
			<moid>moidVal1</moid>
			<r>rVal1</r>
			<r>rVal2</r>
			<r>rVal3</r>
			<r>rVal4</r>
			<r>rVal5</r>
		</mv>
	</mi>
	
	...
	
	<mi>
		<mt>mtVal11</mt>
		<mt>mtVal12</mt>
		<mv>
			<moid>moidVal1</moid>
			<r>rVal11</r>
			<r>rVal12</r>
		</mv>
	</mi>
...
</md>


Note(s): 
	The <mt> and <r> Val pairs can occur within a <mi> node up to 500 instances.

Question:

Basically, the order of tests I need to do is the following:
1 - first match the <moid> value
2 - second match a specific <mt> value
3 - print out the matched <mt> value's corresponding <r> value.

My specific question is when I have matched a <moid> and also matched a <mt> 
value, how do I specify/reference the corresponding indexed <r> value?  In 
the example above, if I match <mt>mtVal4, the fourth element, I would also 
print out the fourth <r>rVal4 value.  

Here's a segment of the current xsl I am using:


<xsl:param name="parm_1"></xsl:param>
<xsl:param name="parm_2"></xsl:param>


=============================================================================
<xsl:apply-templates select="md"/>

</xsl:template>
<xsl:template match="md">
<xsl:apply-templates select="mi"/>	
...
  <xsl:apply-templates select="mv/moid"/>
</xsl:template>

<xsl:template match="moid">
NNN moid node
	<xsl:variable name="moidVal" select="concat(';',.,';')"/>
	<xsl:if test="contains($parm_1,$moidVal)">
		AAA check mt matching val
			<xsl:value-of select="."/>
		<xsl:apply-templates select="../../mt"/>
	</xsl:if>
</xsl:template>

<xsl:template match="mt">
<xsl:with-param name="moid"/>
<xsl:choose>
	<xsl:when test="contains($parm_2,';all;')">
		<xsl:apply-templates select="$parm_1"/>
			AAA print all mts
			<xsl:value-of select="."/>
	</xsl:when>
	
	<xsl:otherwise>
		<xsl:variable name="mtVal" select="concat(';',.,';')"/>
		NNN mt node
			<xsl:if test="contains($parm_2,$mtVal)">
				<xsl:value-of select="."/>
				HOW TO PRINT CORESPONNDING rVal HERE?
			</xsl:if>	
	</xsl:otherwise>
</xsl:choose>
</xsl:template>


</xsl:stylesheet>


Thanks,

=====
Kim

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