The integration of technology in education has provided a more interactive and engaging experience through the creation of Serious Games. By using 3D virtual environments and Virtual Reality, interactive experiences which simulate real-life situations and environments can be created. The development process of such applications often proves to be slow and cumbersome. However, the addition of a trigger system or scenario editor could enable educators to easily create scenarios for students without requiring much programming knowledge. Designing the trigger system should be based on the principles of reusability, applicability and extensibility. This paper focuses on the creation of such a trigger system and its uses throughout the development of a 3D VR Serious game called Visit UPT. This game enables students to explore the university campus and simulate small scientific experiments.