User Exit for Display proposal in F110

Dear Friends,

What is the user exit in F110 to change display of payment proposal : Open items.

Currently it  displaying Co.code,Document#,Currency,Description ,Document type,Posting date,Document date,Posting key,GL Account.

The requirement is it should also display another line item with posting key 40, currently it is displaying only 31.

Both the line item should be displayed just in T.code FB03 (Display document).

Please suggest.

Regards

Sridhar