migrating open gl line item in sap

Hi ,

Can anybody kindly let me know how to pass open vendor line item with following special gl indicator in sap ?

K: Re AP operating Cost

F:Down Payment request.

Becuase i am getting following error while migrating data with special GL indicator F

Special G/L indicator F is not defined here Message no. F5875 Diagnosis The special G/L indicators:

• F (down payment request)

• P (payment request)

are predefined in the system and cannot be changed. Special transactions exist to enable you to create down payment requests and payment requests. The relevant special G/L codes cannot be used except via the appropriate transactions. System Response The system refuses to post the document. Procedure Correct your entry. Use "F" and "P" only for the two transactions listed above.