accumulate a variable...is it possible?

Hi,

I am trying to accumulate a variable but not succesful... here is my xml:
--------------------------------
<numbers>
  <num>3</num>
  <num>7</num>
  <num>11</num>
  <num>6</num>
  <num>3</num>
</numbers>
--------------------------------

here is the output I want:
--------------------------------
num=3 accumulated=3 
num=7 accumulated=10 
num=11 accumulated=21 
num=6 accumulated=27 
num=3 accumulated=30
--------------------------------

here is my stylesheet:
--------------------------------
<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:template match="/">
<xsl:variable name="acc" select="0"/>
<table border="1">
  <xsl:for-each select="numbers/num">
  <xsl:variable name="acc" select="$acc + ."/>
    <tr>
      <td>num=<xsl:value-of select="."/></td>
      <td>accumulated=<xsl:value-of select="$acc"/></td>
    </tr>
   </xsl:for-each>
</table>
</xsl:template>
</xsl:stylesheet>
--------------------------------

here is what I get:
--------------------------------
num=3 accumulated=3 
num=7 accumulated=7 
num=11 accumulated=11 
num=6 accumulated=6 
num=3 accumulated=3
--------------------------------

this post is speaking the same problem, but I want to see the 3, 10, 21, 27, 30 along the way...
http://p2p.wrox.com/archive/xslt/2002-04/57.asp

thanks,
will


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