To enhance the effectiveness of engineering simulations in product development, this thesis presents a new approach that enables designers to include human responses and reactions to artefact behaviour in their investigations. It does so without requiring deployment of real human subjects or investing in interactive virtual environments. The new method introduces scenario bundles, which designers specify as logical instructions that represent their conjectures of how human users react on possible artefact behaviours. During computer simulation, a scenario bundle controls a virtual model of the human user. This control causes intermediate changes in parameters and thus alters the course of the simulated process. The responses specified in scenario bundles can be condition-dependent, so that different concatenated simulations emerge when variations are applied to the product design, to characteristics of human users, and to the surroundings of use. This makes it possible for designers to explore variations of use processes through simulation. The thesis presents the concept and the fundamentals of the method, as well as the development of a proof-of concept implementation of a design support tool. This proof of concept has been successfully tested on a series of sample products.