Problem with selecting UNIQUE attribute

I am building drop downs for the unique values of @names for each directory
at a given level in the following structure along with a list of unique
files types (using file/fileext)

The FileExt drop down works fine and sorts and filters as expected. :-)

It seems that no matter what combination of select expressions I use on the
build-dirlist I am unable to select on the unique values. :-(

I have more than likely been looking at this too long and the answer must be
simple.  Any suggestions on what is wrong with the build-dirlist template ?

<?xml version="1.0" encoding="UTF-8"?>
<dirstruct>
 <dir level="0" name="XML-0.6">
  <file level="0">
   <filename>xml.server</filename>
   <fileext>SERVER File</fileext>
   <filesize>1026</filesize>
   <filelastmod>16/05/2001 11:04:34 PM</filelastmod>
  </file>
  <file level="0">
   <filename>LICENSE</filename>
   <fileext>File</fileext>
   <filesize>26430</filesize>
   <filelastmod>16/05/2001 11:04:34 PM</filelastmod>
  </file>
  <dir level="1" name="bin">
   <file level="1">
    <filename>synergy.jar</filename>
    <fileext>Java File</fileext>
    <filesize>12568</filesize>
    <filelastmod>16/05/2001 11:04:34 PM</filelastmod>
  </file>
  </dir>
... ...
... ...
 </dir>
</dirstruct>

The following template is called via:

... ...
<xsl:call-template name="build-dirlist">
 <xsl:with-param name="LVL">0</xsl:with-param>
</xsl:call-template>
... ...
<xsl:call-template name="build-dirlist">
 <xsl:with-param name="LVL">1</xsl:with-param>
</xsl:call-template>
... ...


<xsl:template name="build-dirlist">
 <xsl:param name="LVL"/>
  <xsl:for-each select="//dir[@level=$LVL and not(preceding::parameter[@name
= @name])]">
   <xsl:sort select="@name" order="ascending" />
    <option>
     <xsl:value-of select="@name"/>
    </option>
  </xsl:for-each>
</xsl:template>

<xsl:template name="build-filelist">
 <xsl:for-each select="//file[not(fileext=preceding::fileext)]">
  <xsl:sort select="fileext" order="ascending" />
   <option>
    <xsl:value-of select="fileext"/>
   </option>
 </xsl:for-each>
</xsl:template>


Kevin


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