Translation Date determination for updating table BSET

Hi all,

The table BKPF has a field called WWERT (Translation Date). We need to calculate the Exchange rate based on the translation date which is in a different period(9). The table BSET has fieds LWBAS (Tax Base in Country Currency) and they must get updated with correct values based on the translation date, but that is not happening as the exchange rate is calculated based on the posting date/billing date(which is in period 12). The exchange rate is determined from the TCURR table but its taking the Exchange rate based upon the document entry/posting date. Could you please help me understand why this is happening since this leading to inconsistency in the ECSL report.