but I only got the value of the first sample in all columns.  Is there a
way of looping through the $columntitles/labels and selecting the sample
where the label matches  in the current row?

Try
<xsl:for-each select="$columntitles">
	<TD>							
		<xsl:value-of select="$samples[label=current()/label]/displayval"/>
	</TD>
</xsl:for-each>

--
Oleg Tkachenko
eXperanto team
Multiconn Technologies, Israel