Add item only for costing in production BOM

Hi 

We person a process bid BOM wherever we adhd a tiny magnitude of liquid created successful location by different section that does not usage SAP. So we don't privation the liquid successful the BOM to make a acquisition requisition oregon accumulation order. We conscionable request the worth of the liquid to beryllium added to the process order's cost. 

How is this possible? I person tried creating the worldly arsenic a benignant NLAG, added it to BOM arsenic benignant N - non-stock item. But past the process bid conscionable seems to disregard it. I cant spot it successful the costing analysis.