How can I retrieve the mass of a single component in the custom properties of my assembly....but after it has been assembly cut?

Basically, what I want is the syntax that is needed in the assembly custom properties to pull the mass of a single component, but after it has been assembly cut

(which means that I don't want to pull the mass from the part document...I want the current mass as it is in the assembly, and I need to use that in my custom properties of the assembly).

It should be something like "SW-Mass@component name@assembly config@assembly filename"  But I can't get that to work.

Does this make sense?

SolidworksAssemblies