I am not sure I understand what you are trying to do.
You can't use the USB connector where the cable comes from the PC as a pin for a sensor. Thats because its attached to the USB controller which you can't really control directly.
If you want to use the usb port to interface to something else, what ever you connect to needs to have a USB host controller, like a PC does, and I am sure ( I haven't researched it yet) you could write your own driver to interface to the host controller.