Mass Properties

Does anyone know a way of having an assembly's weight notinclude certain items that are in the assembly that may be forreference only?
I design attachments for heavy equipment and some of my assembliesshow the machine for reference or design purposes only. However, onthe drawings, I do not want the weight of the machines to beincluded in the attachment weight.
Any suggestions??

GuitarmanSolidworksAssemblies