Same part number, one should be priced and other shouldn't

Hi All

I have an issue in pricing, we have two identical parts, one with configuration and another would by default, ( example, a mirror codes as default, but customer can also choose as an additional item during the confiiguration) . The requirement is one should not be priced where as the second one should. But business wants to bil only one part not the second.

Is there any way to tell the system that if one item is billed anohter should not?

Aany ideas?

Thanks

--Srinivas