The paper proposes a new methodology to interactively simulate grasping of virtual product prototypes with the goal to evaluate the contact forces between the grasping hand and product as well as the load on the human arm. Interaction between product concepts and the users happens in a virtual environment, in which the user controls a virtual hand interactively. The contact between the virtual hand and the grasped product is simulated and visual feedback is provided to the user. Controlling the virtual hand interactively in real time holds many challenges. One of the challenges is mapping the motion of the user to contact forces, which then results in stable grasping of objects. In this paper we present a new methodology to convert and map the measured position of the real hand into contact forces so that the contact between the virtual hand and the object remains stable. Our approach applies a multi-objective optimization that takes into account the posture and anthropometric properties of grasping hand, as well as the penetration of the hand in the grasped virtual object in order to find the optimal arrangement of contact forces. The paper reports on the principle of our grasping control methodology as well as presents some test cases to show the advantages and disadvantages of the proposed approach.