Change fields in IF_EX_ME_PROCESS_REQ_CUST~CHECK

Hi guys

I need to modify a few fields at the time of recording the purchase requisition. I am using the BADI ME_PROCESS_REQ_CUST the method IF_EX_ME_PROCESS_REQ_CUST ~ CHECK, but when I called the method set_data, fields do not change. Anyone know of a solution?