Teritask's message will do what you want.
But I question whether causing the motor to stop because you changed the tab control is a good idea. I wouldn't call that a user friendly GUI experience. When I'm working with tabbed controls in any application, not just LabVIEW, as a user, I don't expect the behavior of the application to change just because I wanted to view a different page, and I certainly wouldn't expect something physical to happen like the shutting down of a motor.
A friendlier user experience would allow a user to view other pages. If they happen to change some configuration values on that page while the motor is running, then when they click an Apply button or something like that, then the application should warn them that doing so will require the motor to automatically stop. Then you'd have an OK/Cancel dialog box to allow them to back out. If they cancel, then the changed values would go back to their original values.
