Split and Found unique values

Hi,
I have an XML like this:

       <target:row Category='A-B-C-D'/>
       <target:row Category='A-B'/>
       <target:row Category='A-C-D'/>
       <target:row Category='C'/>
       <target:row Category='B-C-D'/>
       <target:row Category='A'/>

with a combination of values separated by '-'. I need to populate a listbox
with unique values:

A
B
C
D

I tried to save in a variable what was already processed and skip it in case
was found but the 'seen' variable is clean'd up at the second round:

<xsl:key name='Category' match='xml/target' use='@Category'/>
<xsl:variable name='seen' select="''"/>

  <xsl:template name="my_templ_1">
              <SELECT NAME="X" MULTIPLE="MULTIPLE">
                  <xsl:for-each select='$Rowset[generate-id() =
generate-id(key("Category", @Category))]'>
                     <xsl:call-template name="Split">
                         <xsl:with-param name="strInput" select="@Category"/>
                     </xsl:call-template>
                </xsl:for-each>
              </SELECT>
</xsl:template>

<xsl:template name="Split">
  <xsl:param name="strInput"/>
  <xsl:param name="strDelimiter" select="'-'"/>
  <xsl:param name="processed"/>
  <xsl:variable name="strNextItem"
select="substring-before($strInput,$strDelimiter)"/>
  <xsl:variable name="strOutput"
select="substring-after($strInput,$strDelimiter)"/>

  <xsl:variable name="seen" select="concat($strNextItem,',',$processed)"/>

  <xsl:choose>
    <xsl:when test='contains($strInput,$strDelimiter) and
not(contains($strInput,$seen))'>
      <xsl:element name='OPTION'>
       <xsl:value-of select="$strNextItem"/>
      </xsl:element>
      <xsl:call-template name="Split">
       <xsl:with-param name="strInput" select="$strOutput"/>
       <xsl:with-param name="strDelimiter" select="$strDelimiter"/>
       <xsl:with-param name="processed" select="$seen"/>
      </xsl:call-template>
    </xsl:when>
    <xsl:otherwise>
      <xsl:if test="not(contains($strInput,$seen))">
        <xsl:element name='OPTION'>
         <xsl:value-of select="$strInput"/>
        </xsl:element>
       </xsl:if>
    </xsl:otherwise>
  </xsl:choose>
</xsl:template>

Do you have a more elegant way?

Thank you.
Carlos


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