Pass an xPath as parameter named 'xPathToContent' and evaluate/use that xPath

gistfile1.txt

<xsl:stylesheet version="1.0" 
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

    <xsl:param name="xPathToContent"/>
    <xsl:template match="/">
        <ol>
            <!--   altova has an equivalent 'altova:evaluate'   -->
            <xsl:for-each select="saxon:evaluate($xPathThing)" xmlns:saxon="http://saxon.sf.net/">
                <xsl:apply-templates/>
            </xsl:for-each>
        </ol>
    </xsl:template>
</xsl:stylesheet>