I might TRY setting the recordlocks property of the query to ALL Records. That
should lock up every table involved in the query until the user that called the
query closes it. I don't think that will work too well.
If you are entering data through a form, set the form's Record Locks property to
All Records and that will allow the current user to make changes and lock the
table(s) for all other users until the form is closed.