result-document overwrites previous result

Unlike the output file, the result-document file contains only the last
"Address" processed. My goal is to output addresses in a file other than
the "output file". Can I achieve this using result-document or should I
use a different approach?
To top this, I would like to append to the file if "addressfilename"
exists. Please help this newbie. Thanks.

I am using Saxon 7.9.1 and JDK 1.4.2
The xslt file is-
<?xml version="1.0"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>
        <xsl:param name="addressfilename"/>

        <xsl:output method="text"/>

        <xsl:template match="/">
                <xsl:apply-templates select="Organization/Member"/>
        </xsl:template>

        <xsl:template match="Member">
                <xsl:value-of select="@FirstName"/>
                <xsl:text>|</xsl:text>
                <xsl:value-of select="@LastName"/>
                <xsl:text>
</xsl:text>

                <xsl:if test="$addressfilename">
                        <xsl:result-document
href="file:///{$addressfilename}">
                                <xsl:value-of select="concat(@ZipCode,
'|', @Street, '|', @City, '|', @State)"/>
                <xsl:text>
</xsl:text>
                        </xsl:result-document>
                </xsl:if>
        </xsl:template>

</xsl:stylesheet>