the object of the system presented in this article is to allow experienced designers to describe their knowledge in the way to chain a group of CAD software to resolve a given problem and this, in the form of production rules. This system establish a clear separation between the competencies of the computer scientist, the experienced designer and the final user. It permits the procedure bank of be CAD system to the considered as a group of basic elements from which chaining scenario adapted to the different design problems can be described so as to guide the final user.