overriding a template used in a 'mode'

[Tim Arnold <jtim.arnold@gmail.com>]

hi,
I would like to override part of the chunking xsl stylesheet.

What I've done so far is copy the entire template so it begins as follows:
 <xsl:template match="*" mode="recursive-chunk-filename" priority="1">

and I change on the two parts I want to be different--the chapter and
the section:
 <xsl:when test="self::d:chapter">
   chapter filename stuff
  </xsl:when>
...
<xsl:when test="self::d:section">
   section filename stuff
  </xsl:when>

So my question is whether I really need to copy the whole template or
is it possible to override the original template with a template that
matches just the parts I want to change.

I think the part about this being used in a 'mode' is the part that confuses me.

thanks,
--Tim Arnold