Multiple Sclerosis (MS) is a complex neurological disease that destroys the myelin sheath of the nerves, consequently affecting the motor control ability in numerous ways. It has been shown that people with MS have the potential to improve their functional ability by interacting with robotic training devices through assistive forces. In order to provide a complete and task specific therapy for people with complex neurological impairments, such as those with MS, it is important to take advantage of the robots' ability to provide measurement and force feedback for more complex and realistic 3D motions. The complexity and randomness of natural task-oriented upper-limb motions can be highly preserved in Peg-in-Hole assessment and training methods, such as the widely used Nine-Hole Pegboard Test (NHPT). In the authors' previous work, a virtual NHPT was developed and tested. This paper presents the augmentation of the virtual NHPT with assistive forces in order to become a physiotherapy and rehabilitation system. This system includes target trajectories that are based on the motion of healthy users and adaptive assistive forces that can maximize the benefits from rehabilitation. After development and validation, the system is evaluated on three people with MS. Each participant carried out the NHPT exercise nine times (trials): Initially two trials without application of assistive forces, then five robot-assisted trials (therapy session with application of forces), and two more trials at the end without forces. The results suggest that the system can be effectively employed for rehabilitation in complex movements; nevertheless, its effectiveness must be better grounded with extensive clinical trials.