How to process back dated checks through payment process window in R12

Hi Payable Experts,

             We have a very very urgent requirement. We are trying record checks issued outside the oracle through Payment process manager in R12. The requirement is we want process the checks issue around 1 week back with check numbers.(not autogenerated).What setup need to be done.

       I am able to do this manual checks but we want use payment batch since there are lot of checks and it will be regular process. Please help me asap.

Thanks

kris