Are you trying to find the records in A that do not have any matching records in A2 when you compare product ID and Manufacturer?
If so, this relationship:
A::__pkProductID = A2::__pkProductID AND
A::_fkMfgID = A2::_fkMfgID
Then on a layout based on A, Perform a find specifying an asterisk in A2::__pkProductID, but with the omit options specified.
The found set will be all records in A that do not have a matching record in A2 as specified by this relationship.