Project Portfolio Management (PPM) has become increasingly important in managing multiple projects simultaneously. However, during execution, the project portfolio is associated with considerable uncertainty that leads to resource contention among projects and schedule disruptions. Regarding the need to revise a schedule when unexpected events occur, we adopt an event-driven approach to develop a tradeoff decision framework for project portfolio scheduling and rescheduling. In the framework, High Level Petri nets, Activity-Based Costing and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) are applied in sequence to generate feasible schedules, estimate their makespan and costs, and select the best compromise schedule. This framework is advantageous in the evaluation of scheduling performance from a multi-criteria perspective and the incorporation of both objective and subjective measurements in the decision process.