SQL & PL/SQL :: How To Add Oracle Constraint To Tables

I have three tables:

A {op_id, op_name, .}
B {b_id, op_id, supplier_id, .}
C {c_id, op_id, op_id2, supplier_id, relation, .}

Table B and C have op_id which is foreign key from table A. In table A op_id is primary key, in table B b_id is primary key and in table C c_id is primary key. In table B supplier_id and op_id may have duplicate records. Now I want to add constraint so that if I delete records from Table B for op_id and if a relationship record exists for op_id in table C then it should not allow me to delete. Is it possible through referential integrity constraint ?