What information about GuestID are you storing in your other 2 tables, and
what purpose does it serve???
I can't answer your question without understanding what you're trying to do
with these tables, and why it's necessary to be copying GuestID values to
other tables... rather than just link those tables with a One to Many
relationship through the GuestID.
Let's say you kept a series of RoomServicec transactions for a guest's bill.
You would create a table called RoomSvc, and link them (create a
realtionship) to your Guest table via the unique GuestID. There would never
be a need to copy guest information to the RoomSvc table, because they are
related via the link. Each RoomSvc record has the appropriate GuestID
associated to it, during any new record entry, in the RoomSvc table
automatically due to the relationship... you never have to copy it or enter
it yourself.
Your guest information should be on the main form, and the RoomSvc
information would be on a subform of that form. One guest... Many
RoomService transactions. When a guest arrives, you create a new record for
them, and... as they use Room Services, you add those transactions to the
subform.
Ok I will explain more about my situation..
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I want to make it such a way that when I click on the 'Add Record' button,
the value of GuestID is added in the other two tables as well..