Help with perious ancestor element in loop

Hi all.

Help me please to understood how to be;

i have xml -
<root>
   <val>5</val>
   <val>3</val>
   <val>1</val>
   <val>2</val>
   <val>4</val>
</root>

   <xsl:for-each select="val">
   <xsl:sort select="." data-type="number" order="ascending"/>
      <xsl:value-of select="following-sibling::*[1]/text()"/>
      <xsl:text>|</xsl:text>
   </xsl:for-each>

in xsl i have loop that reordering nodes and work with them.
in loop I want to know previous and next element of the loop order,
in another words previous and next element in nodelist with what work
<xsl:for-each ...

But when i use following-sibling:: axis or another axises it use
original xml but not the nodeset from for-each_select
.

Suggest me, please, how to previous and next element of the loop.

P.S.
Sorry for bad English.

-- 
Best regards,
 Andrey                            mailto:solo@xxxxxxx