CHYP does not have PIN code, thus you can't use it on-line and need to call reservation center. Reservation center should be able to handle both PPDE and CHYP at the same time - it may result different PNR, but they can tie those PNR together on the system.

However, as you may know, restriction and blackout dates of CHYP are significant, totally different from PPDE. Thus you need to pick up dates/fare class which satisfy T&C of CHYP first, then make sure that date/class also falls into PPDE's T&C.

You may want to call CO.COM support desk rather than regular reservation center/desk, to avoid booking fee, since you tried to use CHYP on-line but CO.COM couldn't handle it.