I want to use the MNTP to catagorize nodes/products, to accomplish this I want select a few category-nodes on every node/product. 

On the categorie-pages I want to show the nodes which are relevant/selected for that page. I try to do the following thing in the xslt (with paging):

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE xsl:stylesheet [
  <!ENTITY nbsp "&#x00A0;">
]>
<xsl:stylesheet
  version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:msxml="urn:schemas-microsoft-com:xslt"
  xmlns:umbraco.library="urn:umbraco.library"
  exclude-result-prefixes="msxml umbraco.library">
  <xsl:output method="xml" omit-xml-declaration="yes" />
  <xsl:include href="_pagination.xslt"/>
  <xsl:param name="currentPage"/>
  <xsl:variable name="page" select="umbraco.library:RequestQueryString('page')" />
  <xsl:template match="/">

    <xsl:variable name="matchedNodes" select="$currentPage/descendant::*[@isDoc and selectCategories = 'parentID']" />
    <xsl:variable name="nodeCount" select="count($matchedNodes)" />

    <xsl:if test="$nodeCount &gt; 0">
      <xsl:variable name="page">
        <xsl:choose>
          <!-- first page -->
          <xsl:when test="number(umbraco.library:RequestQueryString('page'))
 &lt;= 1 or string(umbraco.library:RequestQueryString('page')) = '' 
or string(number(umbraco.library:RequestQueryString('page'))) = 'NaN'">
            <xsl:value-of select="number('1')" />
          </xsl:when>
          <!-- last page -->
          <xsl:when test="number(umbraco.library:RequestQueryString('page')) &gt; $nodeCount div $resultsPerPage">
            <xsl:value-of select="ceiling($nodeCount div $resultsPerPage)" />
          </xsl:when>
          <!-- the value specified in the url -->
          <xsl:otherwise>
            <xsl:value-of select="number(umbraco.library:RequestQueryString('page'))"/>
          </xsl:otherwise>
        </xsl:choose>
      </xsl:variable>
      <xsl:variable name="startMatch" select="($page - 1) * $resultsPerPage + 1" />
      <xsl:variable name="endMatch">
        <xsl:choose>
          <!-- all the rest (on the last page) -->
          <xsl:when test="($page * $resultsPerPage) &gt; $nodeCount">
            <xsl:value-of select="$nodeCount" />
          </xsl:when>
          <!-- only the appropriate number for this page -->
          <xsl:otherwise>
            <xsl:value-of select="$page * $resultsPerPage" />
          </xsl:otherwise>
        </xsl:choose>
      </xsl:variable>
      <xsl:if test="$matchedNodes">
        <xsl:apply-templates select="$matchedNodes">
          <xsl:sort select="@createDate" order="descending" data-type="text" />
          <xsl:with-param name="startMatch" select="$startMatch" />
          <xsl:with-param name="endMatch" select="$endMatch" />
        </xsl:apply-templates>
      </xsl:if>
      <xsl:if test="$nodeCount &gt; $resultsPerPage">
        <xsl:call-template name="pagination">
          <xsl:with-param name="page" select="$page" />
          <xsl:with-param name="matchedNodes" select="$matchedNodes" />
        </xsl:call-template>
      </xsl:if>
      </xsl:if>
  </xsl:template>
  <xsl:template match="*[@isDoc]">
    <xsl:param name="startMatch" />
    <xsl:param name="endMatch" />
    
    <xsl:if test="position() &gt;= $startMatch and position() &lt;= $endMatch">
        <div class="product">
            <xsl:variable name="afbeelding1" select="number(afbeelding1)" />
            <xsl:if test="$afbeelding1 > 0">
              <xsl:variable name="mediaNode" select="umbraco.library:GetMedia($afbeelding1, 0)" />
              <xsl:if test="$mediaNode/umbracoFile">
                <a class="layoverlink" title="{@nodeName}" href="{$mediaNode/umbracoFile}" rel="shadowbox[{$currentPage/@nodeName}]"><img src="/images/layoverlink.png" alt="{@nodeName}" /></a>
              <img src="/ImageGen.ashx?image=/{$mediaNode/umbracoFile}&amp;height=125&amp;width=220" alt="{@nodeName}" />
              </xsl:if>
            </xsl:if>
            <h2><a title="Bekijk product" href="{umbraco.library:NiceUrl(@id)}"><xsl:value-of select="@nodeName" disable-output-escaping="yes"/></a></h2>
            <table>
              <tr>
              <td>Prijs:</td>
              <td><b>&#x20AC; <xsl:value-of select="(prijs)" disable-output-escaping="yes" />,-</b></td>   
              </tr>
              <tr>
              <td>Afmetingen:</td>
              <td><b><xsl:value-of select="(afmetingen)" disable-output-escaping="yes" /></b></td>  
              </tr>
              <tr>
              <td>Bekleding:</td>
              <td><b><xsl:value-of select="(bekleding)" disable-output-escaping="yes" /></b></td>  
              </tr>
            </table>
              <span class="green"><a title="Bekijk product" href="{umbraco.library:NiceUrl(@id)}">Bekijk product</a> ›</span>
            </div>
      </xsl:if>
  </xsl:template>
</xsl:stylesheet>

Please help me on this one.