Account assignment of the incoming invoice and the purchase order

Hi,

I am trying to control the account assignment of an incoming invoice against the account assignment of the purchase order used. The link I found is the field ZEKKN. I think RBCO-ZEKKN tells me what account assignment of the purchase order (EKKN-ZEKKN) I am using (just as RSEG-EBELN and RSEG-EBELP help to point the item of the PO used in the invoice). This link is working pretty well in 99% of my Pos and invoices. But sometimes when I create an assignment line in the PO, this line is created with a key EBELN, EBELP, ZEKKN = ‘02’, even if any assignment was created wit an ZEKKN = ‘01’.

In this case, when I park an invoice on this PO, the value of RBCO-ZEKKN is ‘01’ and not ‘02’ as in the table EKKN.

It is very annoying because the control I implement blocks the posting of the invoice..

Any idea or any new link between tables RBCO and EKKN will be very appreciable.

Thanks in advance