The need for interoperability among the rapidly proliferating number of hardwares and softwares led to the definition of CORBA (Common Object Request Broker Architecture). This architecture offers a good interoperability and communication support and the use of such architecture for distributed metacomputing applications seems interesting and promising. However, its implementation is difficult because of protocol diversity and communication modes used by parallel applications. To cure this problem, we develop a message passing library in CORBA environment called MPC (Message Passing in CORBA). In this paper, we quickly present the basic concepts of this library and its broadcast protocol based on the CORBA event service.