Custom Cars Rapidshare NFS Undercover Wii - How Do You Be Custom Cars In Multiplayer Mode?

NFS Undercover Wii - How do you be custom cars in multiplayer mode? - custom cars rapidshare

I want to know whether and how cars can be adjusted (cars are bought and updated Career Mode) in multiplayer mode. This is the Wii version, and you can not load custom cars, but please tell me.
Thanks