In human-human communications, especially in face-to-face communication, sub-verbal and non-verbal messages have more importance than messages transported by words in communications. On the other hand, in traditional man-machine interfaces, machines only understand pre-defined operations, and never understand operators' sub-verbal and non-verbal messages. This causes some difficulty of machine usability. Grasping-and-moving are fundamental hand operations necessary for performing tasks using modern man-machine interfaces. However, behavioral information associated with grasping, such as force, posture, etc., has not been utilized for traditional interfaces. Although behavioral information should have potential utility in developing task-adaptive and operator-adaptive interfaces; it is known that how people grasp devices is dependent on the purpose of these tasks. As an example of typical pointing devices, This work describes a computer mouse whose approaching speed, or gain, is adjusted depending on the nature of the task. This work suggests that the grasping-and-moving tasks should consist of two phases. The first or approaching phase is when the operator moves the mouse pointer close to the target with a small grasping force. The second or positioning phase follows when the operator makes a fine adjustment of the pointer to locate it within the target area using a larger grasping force. This proposed new computer mouse has a sensor to detect the operator's grasping force and uses it to control the gain of the mouse. Two sets of experiments were conducted; one for confirming the assumption that the grasping force should be small while approaching the target and large while positioning, and the other for confirming that the proposed mouse should be effective in reducing the time necessary for pointing various kinds of objects.