FI - MM document link (EKBZ-BSEG LINK)

Hi,

I need to know how can I link EKBZ and BSEG tables ....

I need to know what is the FI document item(BukrsBelnrGjahrBuzei) related to an MM document item (BelnrGjahr+Buzei)

I know that in the FI document we have the link between the FI and the MM document (through the BKPF-AWKEY field).

How can I know the item link?

Please, let me know, it's very important!

I can't make this link through the invoice value .. because I could have 2 lines with the same value ....

Thanks

Lara