xsl:choose; first occurance only

Is there a way to have xsl:choose apply an
action to only the first occurance of an item
and permit the 2nd occurance to be treated
differently?

I know the example I provide below does
not work. Any way to modify it so it does?

Example:

---BEGIN XML---
<?xml version='1.0' encoding='ISO-8859-1'?>
<foo>
<bar>N America</bar>
<bar>Europe</bar>
<bar>Asia</bar>
<bar>N America</bar>
<bar>Europe</bar>
<bar>Asia</bar>
</foo>
---END XML---

---BEGIN XSL---
<?xml version='1.0' encoding='iso-8859-1' ?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:template match="foo">
       <xsl:for-each select="bar">
                        <xsl:choose>
                        <xsl:when test=".='N America'">
        <b>First Occurance</b><br/>
         <xsl:value-of select="." /><br/>
                        </xsl:when>
                        <xsl:when test=".='N America'">
        <b>Second Occurance</b><br/>
         <xsl:value-of select="." /><br/>
                        </xsl:when>
                        <xsl:otherwise>
         <xsl:value-of select="." /><br/>
                        </xsl:otherwise>
                        </xsl:choose>
       </xsl:for-each>
</xsl:template>

</xsl:stylesheet>
---END XSL---
-- 
Bill
Amsterdam, NL

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