Foreign currency PO, how to bypass the system taking standcost X foreign currency rate?

Hello,

When I enter a purchase order with foreign currency, is there is way I can by pass the option of JDE automatically takes standard cost multiply to current currency exchange rate to come up with foreign cost? The foreign cost is a fix pre-determined cost. I would like to retrieve it from a table, may be another cost type in F4105? 

Thank you.