Different vat code required for one plants only in PO for country korea

Hi Team

I have a peculiar situation, in Korea country there are two ,at numbers for different regions, now there is one plant in a particular region having a different vat number then the one maintained in OBY6 for other plants, We want vat number in PO for only one plant should be the one which is there, than the actual vat number number should be which is picked up from OBY6., How to maintain a seprate vat number for only one particular plant differently in PO.

Thanks

Minesh