Thanks all. This is how I solved this problem:
ALTER TRIGGER SPECIMENNO_INSERT
AFTER INSERT
POSITION 0
AS

BEGIN

UPDATE PTDEMOG
SET SPECIMENID = (Select Specno.specimen_no
FROM SPECNO
WHERE SPECNO.PATHNO = PTDEMOG.PATHNO);
END

It seems to work ok. I will continue to test though.
Thanks to all,
hugh

--- In ib-support@y..., PODESTA Mariano APRE <SIDTMPO@S...>
wrote:

> remove the ';' in:
>
> > > > SET SPECIMENID = :counter;
>
> and add it at the end of:
>
> > where ?????? <==========
>
> ie:
> UPDATE PTDEMOG
> SET SPECIMENID = :counter
> where <condition>;