How can you have multiple Custom Property Files and Locations?

Hi,

The company i work for does work with several different vendors and each use there own different custom properties, yet Solidworks wont allow me to add another file location? 

Is there a way to do this or am I going to have to change this each time I go from one customers standards to another?

as you can see its grayed out and won't allow me to add another file location

Regards,