> how could I do the code below with a variable

Just put it inside xsl:variable.

<xsl:variable name="x">
<xsl:choose>
<xsl:when test="something">something</xsl:when>
<xsl:otherwise>
<xsl:text>U N C L A S S I F I E D</xsl:text>
	<xsl:if test="//@secur.dissem='FOUO'">
 	<xsl:text>//FOR OFFICIAL USE ONLY</xsl:text>
	</xsl:if>
</xsl:otherwise>
</xsl:choose> 
</xsl:variable>

then just use

<xsl:value-of select="$x"/>

in two places, rather than searching over the entire document twice.

David


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