Problem using preceding-sibling

Hi,

I try to get the immediate sibling by checking the position, however I get
always the first node.

<xsl:variable name="cpo" select="position()"/>
<xsl:element name="Preceding_GID">
		<xsl:value-of select="generate-id(preceding-sibling::node()[position()=
$cpo - 1])"/>
</xsl:element>

Thanks for any help,
Faroukh

---XML
<Project>
	<Level1>
		<Element1/>
		<Level2>
			<ID>1</ID>
		</Level2>
		<Level2>
			<ID>2</ID>
		</Level2>
		<Level2>
			<ID>3</ID>
		</Level2>
		<Level2>
			<ID>4</ID>
		</Level2>
	</Level1>
</Project>

--- XSLT
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
	<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
	<xsl:template match="/">
		<xsl:apply-templates select="Project"/>
	</xsl:template>
	<xsl:template match="Project">
		<Project>
			<xsl:for-each select="Level1">
				<xsl:call-template name="Level1"/>
			</xsl:for-each>
		</Project>
	</xsl:template>
	<xsl:template name="Level1">
		<Level1>
			<xsl:for-each select="Level2">
				<xsl:call-template name="Level2"/>
			</xsl:for-each>
		</Level1>
	</xsl:template>
	<xsl:template name="Level2">
		<xsl:variable name="GID" select="generate-id()"/>
		<xsl:variable name="cpo" select="position()"/>
		<Level2>
			<xsl:if test="position()>1">
				<xsl:element name="Preceding_GID">
					<xsl:value-of select="generate-id(preceding-sibling::node()[position()=
$cpo - 1])"/>
				</xsl:element>
			</xsl:if>
			<xsl:element name="ID">
				<xsl:value-of select="ID"/>
			</xsl:element>
			<xsl:element name="GID">
				<xsl:value-of select="$GID"/>
			</xsl:element>
		</Level2>
	</xsl:template>
</xsl:stylesheet>

And the wrong result is
<?xml version="1.0" encoding="UTF-8"?>
<Project>
	<Level1>
		<Level2>
			<ID>1</ID>
			<GID>IDAAK42B</GID>
		</Level2>
		<Level2>
			<Preceding_GID>IDAAK42B</Preceding_GID>
			<ID>2</ID>
			<GID>IDACK42B</GID>
		</Level2>
		<Level2>
			<Preceding_GID>IDAAK42B</Preceding_GID>  <! it should be IDACK42B
			<ID>3</ID>
			<GID>IDAEK42B</GID>
		</Level2>
		<Level2>
			<Preceding_GID>IDAAK42B</Preceding_GID>	<! it should be IDAEK42B
			<ID>4</ID>
			<GID>IDAGK42B</GID>
		</Level2>
	</Level1>
</Project>




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