The decision to adopt inter-organisational Electronic Commerce (E-Comm) applications may have unforeseen consequences for the firms involved. It should therefore be taken only after careful consideration of possible implications and pitfalls. In this paper we present a real-life case study of E-Comm investment evaluation, where computer-based models of the business processes to be supported by E-Comm were developed. The models were then dynamically simulated to assist the companies involved in gaining insight on the real benefits and dangers associated with the planned business change.