In this work, a nine-hole peg-board test (NHPT) arrangement is implemented in a Virtual Environment with the use of a Haptic Interface that has the form of a small robotic arm. The Haptic NHPT is used as a mean for investigating the validity of a quantitative metric, which is based on smoothness maximization, as a possible assessment parameter for three dimensional reaching tasks. More specifically this study refers to the assessment of people with multiple sclerosis. The basic metric is developed by combining a neurophysical concept, which suggests that the three dimensional trajectories are piecewise planar, with the minimum jerk model (MJM) which in turn maximizes the smoothness along a predefined path. A total number of sixteen persons participated in the study. From these, nine were healthy young adults and seven were people with MS of various ages and at different stages of disease progress. All participants performed the exercise three times, of which only the second and third were used in the analyses. The results showed that the employed procedure was successful for developing a motion analysis metric for the smoothness in three dimensional trajectories. Also, a clear and traceable difference in performance appeared between the two groups, by using the developed assessment metric.