Hi Wolfgang,
Thank you very much for your reply and your
wise advice to use the \setvariable mechanism. It is indeed much more
convenient to use for what I intend to do.
The only remaining problem is that when
several talks are included in my file (in the following example there
three of them), then the entries to the register are correct but the
associated pagenumbers are incorrect and are given the last pagenumber:
in the following example all three talks are given the pagenumber 4 in
the register. Is there something I am doing wrong?