In this paper, we propose a validation assistant that can assist its users in validating the cooperation and the relationships of messages manipulated by a workstation in a distributed office information system (OIS) modeled by the Office Procedure Model (OPM) to see whether or not the underlying workstation can accurately handle these messages to respond to the occurrence of some specific events. OPM is a formal model that can formally describe and simulate the activities performed by an office agent (a human user) in an OIS. Some unimportant office activities are removed from the OPM diagram to reduce its complexity. A connection matrix representing the simplified diagram is constructed. The algorithm that further partitions the diagram into several message groups to again reduce the scope for easy analysis is also introduced. Finally, for each message group, we set up a Transition Table from which the expressions, in conjunctive normal form, of the objects in the diagram can be derived. Users can inspect the expressions one by one to validate their systems.