DOCBOOK-APPS: [newbie] change a template or add one

[Frederic Alluin <frederic.alluin@webmedia.es>]

Hi everybody,
I want change the html result of a tag (to have one a little bit fun :-)
). So my first tempt was see the docbook.xsl and every other one (glurp!!
....). I don't find the tag so I've made a new xsl file with a simple template
for my tag, and I imported it in docbook.xsl...... But doesn't work =(
So my two questions are:
How can I change a template for a tag defined ??
How can I add a new stylesheet to docbook.xsl ??

Thank you in advance.
Fred