highlighting words/phrases in xml document?

what's the (best) approach using XSL to highlight words and phrases in an XML 
document -- similar to the highlighting of search results in traditional search 
and find?

the phrase and the element inside which to consider the phrase as a hit are 
given as parameters.

thanks for any pointers, or code snippets.  cc appreciated (on digest list).

Jakob.

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list