Sorry I forgot to send the latest XSLT
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:d="data">
<xsl:output method="html" indent="yes"/>
<xsl:variable name ="firstDateTrans">
<xsl:apply-templates select ="Products" mode ="tran1" />
</xsl:variable>
<xsl:variable name ="lastDateTrans">
<xsl:apply-templates select ="Products" mode ="tran2" />
</xsl:variable>
<xsl:template match="/">
<select id="selDate">
<xsl:call-template name="month-list">
<xsl:with-param name="start" select="floor($firstDateTrans div 100)"/>
<xsl:with-param name="end" select="floor($lastDateTrans div 100)"/>
</xsl:call-template>
</select>
</xsl:template>
<xsl:template name="month-list">
<xsl:param name="start"/>
<xsl:param name="end"/>
<xsl:if test="$start <= $end">
<xsl:variable name="year" select="substring($start,1,4)"/>
<xsl:variable name="month" select="number(substring($start, 6, 2))"/>
<option value="{concat($year, '.', $month)}">
<xsl:value-of select="concat(substring('JanFebMarAprMayJunJulAug SepOctNovDec',($month - 1)*3+1, 3), ' ', $year)"/>
</option>
<xsl:variable name="next-month">
<xsl:choose>
<xsl:when test="$month=12">
<xsl:value-of select="($year+1)*100 + 1"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="$start + 1"/>
</xsl:otherwise>
</xsl:choose>
</xsl:variable>
<xsl:call-template name="month-list">
<xsl:with-param name="start" select="$next-month"/>
<xsl:with-param name="end" select="$end"/>
</xsl:call-template>
</xsl:if>
</xsl:template>
<xsl:template match ="Products" mode ="tran2">
<xsl:for-each select ="Product">
<xsl:sort select ="@lastIns" order="ascending" data-type="text"/>
<xsl:if test ="position()=last()">
<xsl:value-of select ="number(translate(@lastIns, '-', ''))"/>
</xsl:if>
</xsl:for-each>
</xsl:template>
<xsl:template match ="Products" mode ="tran1">
<xsl:for-each select ="Product">
<xsl:sort select ="@firsIns" order="ascending" data-type="text"/>
<xsl:if test ="position()=1">
<xsl:value-of select ="number(translate(@firsIns, '-', ''))"/>
</xsl:if>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
And this is the XML
<Products>
<Product prodID="PRD0099" name="Azasan" class="Transplant/Immunosupp" company="Aai Pharma" firsIns="2003-03-01" lastIns="2004-12-31" />
<Product prodID="PRD0215" name="Darvocet A500" class="Propoxyphenes" company="Aai Pharma" firsIns="2003-02-01" lastIns="2005-09-30" />
</Products>
