I see!!!!!
<q>because it is one run of the XSLT engine the value returned for a given
node is guaranteed to be the same. </q>

Hence I can use it twice in the same stylesheet and 
get the same number.
timewise I'm referring to an id that hasn't been written (yet).

Though when the html comes out they are both there!
(Flash of light!)

Many thanks Ken.
I'll add that to the FAQ.
regards, DaveP


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