AW: Accessing values in a node-set using XPATH

Hello,
I would like to display only the values of an XML that are configured in a
separate Configuration file. As the data is structured it makes sense to
access the data using an XPATH. This can be done using dyn:evaluate() like in
the example below.

<xsl:template name="print">
   <xsl:param name="pos"/>
   <xsl:variable name="xpath">
      <xsl:value-of
select="document('config-szenario.xml')/config/Line/field[position() =
$pos]"/>
   </xsl:variable>
                       
   <xsl:if test="$xpath">
       <xsl:variable name="valueofxpath">
             <xsl:value-of select="dyn:evaluate($xpath)"/>
       </xsl:variable>  
                                               
       <td>
          <xsl:value-of select="$valueofxpath"/>
       </td>
                                   
       <xsl:call-template name="print">
           <xsl:with-param name="pos" select="$pos + 1"/>
       </xsl:call-template>
   </xsl:if>
</xsl:template>
                                                 
However is there a possibility to perform this also on a nodeset? I would like
to pass a variable (e.g. comparing) and then call dyn:evaluate like shown
below. However it raises an error. It this somehow possible?

<xsl:value-of select="dyn:evaluate($comparing/$xpath)"/>

Thank you in advance
            Dagmar