[xsl] how to store node in variable?

[John <john-xsl-list@xxxxxxxx>]

Sorry to trouble the list with this one which seems so simple and yet 
somehow I am banging my head against the wall for hours and I can't even 
think what to search for.  The worst part is I think I've done this 
before...

How do I store a reference to a node in a variable or what am I doing 
wrong?  Here is what I have (maybe oversimplified) :

<xsl:variable name="me">
  <xsl:choose>
    <xsl:when test="<some condition>">
      <xsl:copy-of select=".." />
    </xsl:when>
    <xsl:otherwise>
      <xsl:copy-of select="." />
    </xsl:otherwise>
  </xsl:choose>
</xsl:variable> 
<xsl:call-template name="<some template>">
  <xsl:with-param name="myid" select="$me/@id" />
</xsl:call-template>

The with-param is always throwing an error, expression should result in 
a node-set.

If I add msxsl:node-set around my selects in the variable definition I 
get cannot convert result tree fragment to node-set.

Alternatively, is there any way to explicitly set the context node 
without using for-each?

Again my apologies.

-John