Nowadays, it is common to see the use of a network of machines to distribute the workload and to share information between machines. In these distributed systems, the scheduling of resources to applications may be accomplished by a Resource Management System (RMS). In order to come up with a good schedule for a set of applications to be distributed among a set of machines, the scheduler within an RMS uses a model to predict the execution time of the applications. A model from a previous thesis was analyzed and refined to estimate the time that the last task will be completed when scheduling several tasks among several machines. The goal of this thesis was to refine the model in such a way that it correctly predicted the execution times of the schedules while doing so in an efficient manner. The validation of the model demonstrated that it could accurately predict the relative execution time of a communication- intensive, asynchronous application, and of certain compute-intensive, asynchronous applications. However, the level of detail required for this model to predict these execution times is too high, and therefore, inefficient.