A plan-based approach for systems that support office activities involving multiple agents has several advantages. It can represent important aspects of these activities, it has the potential for alleviating maintenance problems by generating new plans when activities change, and it can increase the reusability of knowledge across activities. On the other hand, because office activities take place in dynamic environments a system using a plan to coordinate an activity will have to deal with many contingencies and surprises. We describe the main characteristics of a plan-based approach and the roles a system of this kind can play in an office, and present a process for handling contingencies which can make the system robust in the presence of contingencies not explicitly dealt with in the plan. We close with a discussion of an implementation of the process and the viability of the approach to support real office activities.