MS Access97 referential integrity

I need to use complex foreign key, some
fields of this is not required. Simplified
example showed below (in real database values of required fields defines by another foreign key)

CREATE TABLE A
(F1 TEXT(3) NOT NULL,
F2 TEXT(3) NOT NULL, INFO TEXT(32) NOT NULL,
CONSTRAINT PK PRIMARY KEY (F1,F2));

CREATE TABLE B
(F1 TEXT(3) NOT NULL,
F2 TEXT(3) NULL,
INFO TEXT(32) NULL,
CONSTRAINT FK FOREIGN KEY (F1,F2) REFERENCES A(F1,F2));

In MS Access 97 I can’t insert into table B
values (‘001′,NULL,’INFO’) – error 3201 generated. In MS Access 2.0 such insert is
allowed. Can I tune MS Access 97 to allow this input – Thank you.