Passing custom fields to BAPI

Hi All,

How can i handle the Quantity field using BAPIPAREX?

EX.

I have added the following custom fields to the standard table EKKO.

zf_base (Price per ton, CURRENCY)

zreq_tons (Tons Required,QUANTITY)

zpo_issue_date (PO Issue date,Date)

Here I am using the bapi 'BAPI_PO_CREATE1' to create Purchase Order. How can i pass the above fields to BAPI.