creating a flat file in the IDOC format

Hi everybody,

Need help.....urgently. Can somebody please tell me how to create a flat file in the IDOC format? I am creating a bill of lading/Documentary payments (EDI 858) and can't figure out a way to write the data generate through the report in a flat file in IDOC format. My deadline is right around the corner and I need help.

Thanks,

M