Most simulation studies of context-aware systems have not involved the aspect of changes of the environment or users' context, notably changes triggered by the elapse of time or users' own action. We proposed an evaluation method to simulate user operations with a user model in which the user preference or the user context changes based on events such as sensor information or the user's actions. Through implementation of an evaluation system for a drive planner system, we confirmed a virtual user's action and acquired directions for evaluation of context-aware systems.