Why can't I do something like this?B But below one i*s NOT working .. *

*I need to know how to select amount based on the supplied order num: *
 B  B  <xsl:value-of
select="$Orders_Part2/orders*/order_num[$ordernum]*/amount"/> ==> not
working

If the key use in my original XSLT 1 suggestion seems too complicated
then use plain XPath

<xsl:template match="order">
  <xsl:copy>
    <xsl:apply-templates select="@* | node()"/>
    <xsl:apply-templates select="$doc2//order[order_number =
current()/order_number]/amount"/>
  </xsl:copy>
</xsl:template>

But don't come along tomorrow or next week and complain that it doesn't
perform well on larger input documents.