BAPI_ACC_DOCUMENT_POST with two currencies

Posting a document using BAPI_ACC_DOCUMENT_POST, I had used de BAPIACAP09 structure - ACCOUNTPAYABLE - to make an employee payment.

This structure forces a different payment currency to the one used in the document.

Could you tell me how can I program the system to use only one type of currency, I mean, how I can use this function and this structure so it allows me to use the same type of currency?