The technical and academic aspects of the Event-B method , and the abstract description of its application in industrial contexts are the subjects of numerous publications. In this paper, we describe the experience of development engineers non familiar with Event-B to getting to grips with this method. We describe in details how we used the formalism, the refinement method, and its supporting toolset to develop the simple anti-collision function embedded in a small rolling robot. We show how the model has been developed from a set of high-level requirements and refined down to the software specification. For each phase of the development, we explain how we used the method, expose the encountered difficulties, and draw some practical lessons from this experiment.