Thanks! I had tried using it but must have had something else wrong.

Ken>The XSLT current() function points to the current node at the start
of the XPath expression.

Ken>     <xsl:template match="w">
Ken>         Value: <xsl:value-of select="key('fruit', @x)/b/
Ken>         c[@d = current()/@y and .=current()]/../c[@d eq
current()/@z]"/>.
Ken>     </xsl:template>