Hi Anil,
As per my understanding, you need to write the custom logic in the FM FI_PAYMEDIUM_DMEE_20 and FI_PAYMEDIUM_DMEE_30 which has new fields in the structure ( might be Importing or tables ) parameters. If it is the case choose Implicit enhancement to derive your code at the top or bottom.
Please revart back if my understanding is wrong, much clear with your issue.
With Regards,
Giriesh M