Passing Parameters to xsl:sort

I am trying to pass a parameter to control the sorting of report output. I
can pass the parameter to the 'order' attribute, but passing a parameter to
the 'select' attribute does not seem to work.

<xsl:param name="order">descending</xsl:param>
<xsl:param name="sort-value">trunk-group-type</xsl:param>

 ...

<xsl:sort select="$sort-value" order="{$order}"/>



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