<?xml version='1.0'?>
<!DOCTYPE xsl:stylesheet SYSTEM "file:///C:/C64/home/ht/lib/xml/xsl.dtd" >
<xsl:stylesheet xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:e="http://markup.co.uk/excel" version="3.0">
 <xsl:variable name="codeBase" select="string-to-codepoints('A')-1"/>
 
 <xsl:function name="e:n2aa" as="xs:integer*">
  <!-- Does the real work for e:n2a -->
  <xsl:param name="n" as="xs:integer"/>
  <xsl:sequence select="let $least := $codeBase+(($n - 1) mod 26)+1
                         return if ($n &lt; 27) then $least
                          else (e:n2aa($n idiv 26),$least)"/>
 </xsl:function>

 <xsl:function name="e:n2a" as="xs:string">
  <!-- Invert the a2n computation -->
  <xsl:param name="n" as="xs:integer"/>
  <xsl:value-of select="codepoints-to-string(e:n2aa($n))"/>
 </xsl:function>
</xsl:stylesheet>