Inertia Tensor of a group of pieces (assembling)

Hi Guys,

When I design a isolated piece on SolidWorks I can evaluate easilythe inertia tensor of the piece, but in the assembling mode thesoftware returns me only the mass of the assembly. How can Idetermine the inertia tensor of an assembling?

Thanks,

PralonSolidworksAssemblies