Product Costing

Hi,

i have a row material that is receipt with different cost against the voucher. Before voucher arrived this row material is issued for a finish good. How can i include the real cost(voucher cost) in finish good cost?

For example:

Receipt row material ( Item A cost= 1$). Manufacture finish good (item B cost= 1$ +cost components). The voucher come and the cost for item A is 2$. The cost for item B should be 2$+cost component.

Thanks, Laurentiu