ABAP code issue

Hello Experts,

need a help to write ABAP code  in sap-bw environment.

My requirement is to calculate Daysoverdue (number or integer) from two dates. (lot end date and date of usage decision).

My two date fields are there in masterdata talble)In BW it is /BIC/PINSP_LOT . so i need to read this table to get lot end date and date of usage decision  and will perform calculation.

ex: (0INSP_LOT__LOPENDD – 0INSP_LOT__LOEUDC) * (-1).

so how to achieve this? If possible please provide some the code. Required your valuable inputs.

regards,

Raki.