user exit function module include how to write the code

hi all,

i am creating user exit for ME22N using this enhance MM06E005 .

in this i created subscreen and set some fields .

that data has to be stoe in EKPO.

inside the include i have to write the logic plz guide me how to follow .

once i enter it will store on wish internal table and wish internal table to shall i move to EKPO .

If Tcode is ME23N how to display data in disable mode.

Regards,

Hari.