xslt - XSL 1.0 unique values from variable -

i not familiar xsl , writing code has variable:

    <xsl:variable name="rows" select="/dsqueryresponse/rows/row[(contains(normalize-space(@state.),$state) or string-length($state) = 0) , (contains(normalize-space(@event_x0020_display_x0),$month) or string-length($month) = 0) , (contains(normalize-space(@event_x0020_type),$eventtype) or string-length($eventtype) = 0)]"/> 

i need use variable populate 3 dropdownlist unique values. have tried several thing , code below work if page load values. if filter using parameter values in dropdown gets mess up.

<td class="ms-vh" nowrap="nowrap"> <select name="select1" style="width:200px;">    <xsl:for-each select="$rows">     <xsl:sort select="@state"/>      <xsl:if test="not(@state=preceding-sibling::row/@state)">         <option>            <xsl:value-of select="substring-after(@state,'#')" />        </option>      </xsl:if>    </xsl:for-each> </select> </td>