project cost

Hi PS experts,

I have a requirement. some materials come from our customer, we purchase them by free of charge PO, then we will install them to our machine. after our machine finished, we will deliver to our customer within customer materials. SO, these customer goods are free when goods receive and goods issue, no invoice generate. But, these material's cost has been post to related project. it's not reasonable. so could you please help me to give solution or suggetion to solve this problem? Thanks in advance!

Waiting for your reply!!

Grace