start / stop usb

How can usb be started and stopped in 9.3 or 10.0? I always thought that this can be accomplished through the rmmod command, given as su or root. I need to stop at least usblp, ehci_hcd , ohci_hcd and usbcore, in order to allow a vmware virtual machine to take over a port to install a printer driver. It seems that everything except usbcore can be removed, but not usbcore. thanks in advance, d