We have investigated aspects of the design of Problem Solving Environments (PSE) by constructing a prototype using CORBA as middleware. The two issues we are mainly concerned with are the use of non-trivial (containing more than just a start method) CORBA interfaces for the computational components, and the provision of interactivity using the same mechanisms used for flow control. After describing the design decisions that allow us to investigate these issues, and contrasting them with alternatives, we describe the architecture of the prototype and its use in the context of a study of photonic materials. We argue that having several methods on a component interface can be used to mitigate performance problems that may arise when trying to solve problems in PSE's based on small components. We describe how our mechanism allows a high degree of computational steering over all components.