Reading Archived data into abap BAPI_AR_ACC_GETKEYDATEBALANCE

HI ,

     i modifying a custom report to display the archived data .while doing i am encountered with  the BAPI : BAPI_AR_ACC_GETKEYDATEBALANCE,which will fetch the opening balances form table bkpf .in my scenario we archivied the bkpf table data with fi_documnt object  ,so, the bapi is not giving the open balance for the vendor in the custom report . how to get the opening balances which are archived, in to abap .

Note : post-processing is not done for fi_documnt .

Regards ,

Krishna .