Since Hans sent me his examples I've been further checking my
Training Database.

I had defined a Foreign key constraint on DETAIL.ID with reference
to MASTER.ID with cascade on Update.

If I remove this constraint from DETAIL then I'm able to insert a
new record into MASTER and new records into DETAIL without any
problems.

I'm not too happy with this solution since it seems to me to be
sidestepping an important database integrity check.

There must be a way of keeping the Foreign Key contstraint and at
the same time intercepting the DETAIL record's posting attempt to
deal with the MASTER table which has not as yet been posted.

It doesn't help intercepting the BEFOREPOST event in DETAIL and
forcing the MASTER to post since this causes the DETAIL record to
vanish again.

Any help will be greatly appreciated