How do i change the default cable root letter?

When I assign a cable to a wire it designates it with "W" and a number.  I found the formula for setting the cable marks and its setup as:

CABLE_ROOT + CABLE_ORDERNO

I know i can just change this formula to put any letter I want in replacement of the root.  My question is though where can I change the default value of "CABLE_ROOT".  Like components, I can go to Library/Cusomization/Component classification, and I can set all the default designator root values of components based on their class.  Is there anywhere like this that I can change the root value for cables?

Thanks,

Zac

SolidworksElectrical