[xsl] check if document exists

["Rick Roen" <Rick@xxxxxxxxxxxxxxxxxx>]

I'm trying to check if a document exists before I do something in a XSL 2.0
stylesheet, however it fails using XML Spy:


			<xsl:variable
name="postnetfile">.\postnet<xsl:value-of
select="../@zip"/>.png</xsl:variable>
			<xsl:choose>
			
			<xsl:when test="boolean(document($postnetfile))">
			<fo:block padding-left="3mm" padding-top="5mm">
found postnet file
				<!--<fo:external-graphic><xsl:attribute
name="src"></xsl:attribute></fo:external-graphic>-->
			</fo:block>
			</xsl:when>
			</xsl:choose>

Result: "XSL transformation failed ue to the following error: Error in XPath
2.0 expression Error retrieving resource - 'C:\temp\postnet94030.png'

Can someone tell my what is wrong?

Rick