Setting orders05 field PARTN

Hi all,

I have the requirement to send purchase orders with IDOC type ORDERS05. Our vendor expects
his customer number in segment E1EDKA1 at the fields "PARVW = AG" and "PARTN = Customer number".
In my structure PARTN is initialised with "1000".

In which table I can define the setting ? Is there any chance to define a dependency to our ordering plant in the purchase order ?

Thanks a lot in advance.

Best regards

Christoph