> well if you want it purely in the template match for <s> then you can do:
> 
> match="s[(ancestor::b[1]//text())[last()] >> .]"
> 
> ...but there's probably a neater solution where you work it out at the
> <b> level and then pass down a boolean as a tunnelled parameter.
> 
Thanks a lot for this solution which works like a spell and also taught
me the ">>" operator. In the given context I prefer it to Ken's
procedural solution, but also thank you for that one.