How to generate external <topic> using eclispe.xsl?

I'm using the eclipse.xsl stylesheet to successfully transform DocBook
XML into *.html files and a corresponding toc.xml for the
documentation for an Eclipse plug-in.

I would like to add an external URL (not an href to a local document)
as a topic in the toc.xml:

<topic href="http://www.example.com/news.html" label="Latest News"></topic>

I can manually add the topic to the generated toc.xml with no problem,
but each time the transformation of the DocBook document is done, the
toc.xml gets replaced, and I have to manually add the topic again.
Ideally, the topic would be automatically included in the generated
toc.xml, but I cannot find either a DocBook element or a parameter
tweak for eclipse.xsl that will insert the desired topic (I am
definitely not an XSLT guru).

Any experts out there with a suggestion?