COPA posting

Hello Gurus,

We are using costing based copa. I have a question on COPA posting. I have a sales order with 3 line items. During the billing document creation, 3 COPA documents are getting generated with amounts assigned to COGS Material value fields. There is no amount against the revenue value fields Our business user wants to stop generating COPA document in this case as there is no revenue on the sales order. Is it possible to stop generating the copa docs just because we do not have revenues? Where is the mapping of VVMAT field with cost estimates? Thanks in advance.

Thanks