Update primary key with sequence number

To dynamically set a primary key column to a sequence number, add a page process that fires 'On Submit - After Computations and Validations' before the 'Process Row of [table]' process.
Use a PL/SQL statement that selects the sequence.nextval into the primary key column:

if :P3_EMPNO is null then
select ct_id_seq.nextval into :P3_EMPNO from dual;
end if;

Make sure to use the if statement. If you don't then you will encounter No-data-found errors.