The tokenize function belongs to XSLT 2.0, you cannot use it in the XSLT 1.0 product you are using. If you want to use it, and other XSLT 2.0 functions, you will need to use a transformer that supports XSLT 2.0. Saxon is one, and there may be others.
Or if you want to stick with the transformer you are using now, just google for "xsl tokenize". When I did that I got at least four web pages explaining how to do it. [ August 20, 2007: Message edited by: Paul Clapham ]