Most firms rely mainly on the PERT method (with or without CPM/PERT COST) for project planning. Some use a structured PERT via the work break-down structure approach. This paper examines how this classical procedure could be improved. In the MPSP model, the project structure identified during the functional decomposition phase is used as a support for a piloting system meant to assist the project manager during all the project's lifetime. The model views a project as a hierarchy of functional states (f-states) communicating with each other via the functional links: in it, the functional structure gets a new dynamic, real-time use. Eachf-state's evolution along the project lifetime is modelled as that of a finite state automaton: its input alphabet is made up of the signals indicating the presence of input documents and/or products necessary to thef-state's operations and its output alphabet comprises all the intermediate output it produces. The model associates one PERT graph with each terminalf-state but it does not enforce precedence rules across terminalf-states as does WBS. The necessary intercommunication is made possible by the use of control signals circulating through the functional network and communicating the presence of specific events. The project manager using MPSP can follow-up eachf-state's evolution and control an effective and smooth production of all intermediate outputs.