If you are lucky (and the Customizing of field status variant helped) you can find EBELP/EBELN in the item BSEG structure. (Ask FI/MM functional)
Else there can be link between BKPF and EKKO depending on AWTYP
- 'MSEG' -> BKPF-AWKEY -> structure MKPF_AWKEY -> MKPF keys -> MKPF -> EKPO
- 'RMRP' -> BKPF-AWKEY -> concatenation of RBKP-BELNR, GJAHR -> RBKP -> EKPO
From MM, you could also use EKBE table
Regards,
Raymond