read/write in the same xml file

[abbouh <ab...@ra...>]

I try to read from the  xml file "compte.xml"
and to write in the same xml file,but i find that the xml file wasn't
modifided.
this is my xml file:

<document>
<compte>25</compte>
</document>



this is my xsl file:

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:lxslt="http://xml.apache.org/xslt"
xmlns:redirect="org.apache.xalan.xslt.extensions.Redirect"
extension-element-prefixes ="redirect">
<xsl:output method="text" version="1.0" encoding="ISO-8859-1"
indent="yes" omit-xml-declaration="yes" />
<xsl:param name="file_cnf" select="'compte.xml'"/>


<xsl:template match="/">

<xsl:variable name="refdoc" select="document($file_cnf)"/>

<xsl:variable name="vcompte">
<xsl:value-of select="$refdoc/document/compte"/>
</xsl:variable>

<redirect:write file="$file_cnf" method="text">
          <document>
          <compte>
          <xsl:value-of select="$vcompte + 100"/>
          </compte>
          </document>
</redirect:write>

<xsl:value-of select="$vcompte + 100"/>
</xsl:template>
</xsl:stylesheet>


i should have in xml file at the end:
<document><compte>125</compte></document>