Web services have emerged as a de facto standard for encapsulating services within or across organization boundaries. Various proposals have been made to compose Web services into workflow so as to meet the goal previously unaccomplished by a single entity. This paper focuses on the workflow access control problem and proposes a Web service selection approach that dynamically chooses a performer for each task in the workflow, not only to satisfy all access control constraints currently but also to increase the chance of completing the entire process in the future. The proposed approach is evaluated using synthetic data and is shown to result in the execution that is less likely to violate any specified access control constraints.