I have never tried putting a for-each inside a variable, but if that is possible in the specs, could you then not do something like:

<xsl:variable name="SorterList">
 <xsl:for-each select="report-root/txns">
   <xsl:sort select="cpmBI"/>
   <xsl:sort select="date"/>
</xsl:variable>

<xsl:variable name="SortList2" select="document('')/xsl:stylesheet/xsl:template/xsl:variable[@name='SortList']/cpmMemBI"/>

Then loop trough SortList2 and get the values of the current and preceding cpmMemBI element?

I don't know if this is at all possible (and if the syntax should differ), but I think this would be easier than a two-pass solution.

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