You last question is in fact the "key" to making this work. You may not, in fact, need a Field 4 at all in Table A. The relationship would look identical to what you have posted:
table A:: field 1 = table B::field 1 and
table A:: field 2 = table B::field 2 and
table A::field 3 > table B::Field 3
In Manage Database, you can drag from field 1 in table A to field 1 in table B, then do the same to link Fields 2 and 3. Then double click the relationship line ot open a dialog where you can change the = operator to > for the Field 3 pair of match fields.
Then, with that relationship in place, you can use the field tool to add Table B::Field 4 directly to your layout and it will display data from Table B whenever the values in FIelds 1, 2 and 3 match as specified in the relationship.