Request Documents 
Program RFBIBLK0 posts request documents into the system that have been created outside the SAP system.
For detailed information, see the program documentation Request Transfer from Preprocedure (RFBIBLK0).
If you want to transfer requests from preprocedures into your SAP system, you have to call the data transfer workbench (transaction SXDA) and select the object type accounting document (BKPF).