Display order issue

Current display:
American journal of cardiology 
MDConsult (Full-Text), Elsevier (Full-Text) 

Desired display:
American journal of cardiology 
Elsevier (Full-Text), MDConsult (Full-Text) 
 
XML input:
<B1>American journal of cardiology</B1> 
<B2>MDConsult</B2> 
<B2>Elsevier</B2> 
<B3>http://home.mdconsult.com</B3> 
<B3>http://www.sciencedirect.com</B3> 
<B7>2</B7> 
<B7>1</B7> 

Note: The first occurance of B2 is related to the first occurance of B3
(which is the URL for the text "Full-Text") and B7 (the priority display
order).  The second occurance of B2 is related second occurance or B3
and B7...etc. 

XSL Code:
<xsl:for-each select="$items[name()='B2']">
     <xsl:variable name="pos" select="position()"/>
     <xsl:variable name="url" select="following-sibling::B3[$pos]"/>
     <xsl:value-of select="."/>
         <xsl:text> (</xsl:text><a
href="{$url}">Full-Text</a><xsl:text>)</xsl:text>
         <xsl:if test="position()!=last()">
         <xsl:text>, </xsl:text></xsl:if>
</xsl:for-each>

Any ideas how to solve this?

Thanks in advance!

Joseph

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list