grr it's much easier (in general) if you post a complete stylesheet.

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">

<xsl:variable name="Doc1" select="document('doc1.xml')/Input/I"/>
<xsl:variable name="Doc2" select="document('doc2.xml')/A/B"/>

<xsl:template match="/">
<Output>
 <xsl:for-each select="$Doc2/@*">
 <xsl:copy-of select="."/>
 <xsl:copy-of select="$Doc1/@*[name()=name(current())]"/>
 </xsl:for-each>
 <xsl:text>Some text in the output element</xsl:text>
</Output>
</xsl:template>

Best regards,
Ragulf Pickaxe :-)