In this paper, we propose an internal protocol assistant that can help users to verify and validate the cooperation and the relationships of the messages exchanged among agents in a distributed office information system to see if internally the underlying agent can work properly or not when some specific events occur. Office Procedure Model (OPM), which is the formal model of the concerned agent in an office information system, is used as an example. A connection matrix is constructed to represent the OPM diagram. The algorithm for partitioning the OPM diagram into several message groups to reduce its scope (called Indivisible Cut Zones) is also introduced. Finally, for each message group we set up a Transition Table from which the expressions of the objects in ,the diagram can be easily derived. Users can inspect the expressions one by one to verify and validate their systems.