Help in implementing date logic calculation

Hello,

We need to implement below logic in our Webi report:

Report Logic: Any Purchase_Order whose delivery (Promised Date) is pending next in 15 days and also any pending deliveries which has not happened beyond 15 days.

Please suggest how the above logic can be implimented at the report level or at the Universe level.

I have tried with below object at the universe level but it is not giving correct results.

case when (sysdate - DWH_SSS_PO_LINE_LOC_DETAILS.PROMISED_DATE>=15) or (DWH_SSS_PO_LINE_LOC_DETAILS.PROMISED_DATE-sysdate<15 ) and DWH_SSS_PO_LINE_LOC_DETAILS.QUANTITY_RECEIVED=0 then 'Y'  else 'N' end

It is BOXI3.1 SP7 on Oracle 11g db.

Thank you.

Regards,

Kaustubh Ghate