How to copy the previous operations?

Hi,
 Can anyone help me out how to copy the previous operations?
The xml source would look like this:

<formatted-xml>
  <group><identifier>a</identifier>
   <signature>signature <identifier>DNSQuery1</identifier>
     <in>in<long>long</long><identifier>ant</identifier></in>
   </signature>
  </group>
  <group><identifier>b</identifier><identifier>a</identifier>
    <signature>signature<identifier>DNSQuery2</identifier>                
       
     
<inout>inout<string>string</string><identifier>grass</identifier></inout>
    </signature>
  </group>
  <group><identifier>c</identifier><identifier>b</identifier>
     <signature>signature<identifier>DNSQuery3</identifier>               
        
       <out>out<boolean>boolean</boolean>
<identifier>fish</identifier></out>
     </signature>
  </group>
</formatted-xml>

    What I have to do is, I should copy the signature part the first group
identifier 'a' to the signature part in group identifier 'b', because it
is followed by the group identifier 'a'.
    Similarly, the third group identifier 'c' is followed by the second
group identifier 'b' (which should have already copied the 
first group identifier a's signature part) and so the second group
identifier's signature part should be copied to the third group identifier
signature part.

I tried the following xsl.

<xsl:template match="group">
  <xsl:if test="identifier[2]= preceding::group/identifier">
     <xsl:copy>
        <xsl:apply-templates select="preceding::group/signature"/>
     </xsl:copy>
  </xsl:if>
</xsl:template>
 
  But it didn't work.

Thanks and regards,
Ram


__________________________________
Do you Yahoo!?
Protect your identity with Yahoo! Mail AddressGuard
http://antispam.yahoo.com/whatsnewfree

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