1. An implantable medical device (IMD) for providing an electrical neurostimulation therapy to a neural structure of a patient's body and a predetermined response to a magnetic field, comprising: a sensor to detect the presence of a magnetic field; a controller operatively coupled to said sensor, said controller programmed to implement said predetermined response in response to a detection of said magnetic field; and an interface to receive an override signal for placing said IMD into an override mode; wherein said controller is operatively coupled to said interface, and said controller is programmed to block said predetermined response to said magnetic field for a preprogrammed period of time in response to receiving said override signal.