I am using purchased version of Saxon v126.96.36.199 and have instances of saxon:evaluate() already in my code. I'm trying to trap expression syntax errors from within the XSL stylesheet before my saxon:evaluate() functions are called. Any suggestions?
Try using the namespace http://saxon.sf.net/ for saxon:
If this still doesn't work, you might be using Saxon HE where the saxon extensions are not available any more. Either revert to Saxon 9.1 or purchase the commercial product Saxon PE (recommended, particularly because some bugs have been fixed in the meantime).