Costing for 2 processes customization

Hi Experts,

I have item A which is cost 20 Cents and it purchase from supplier A. So my work flow will be PO->GPO->OutGoing But later on the item A will be send for supplier B for customization and will cost 40 Cents. So this work flow also like PO->GPO->OutGoing .

Problem how much is my total cost it will be 60 Cents but if i do it as PO->GPO->OutGoing , the cost will be overwrrite to become 40 Cents.

PLease kindly advise.

Thanks.

Regards,

Danny