Creating Web processes using Web service technology gives us the opportunity for selecting new services which best suit our need at the moment. Doing this automatically would require us to quantify our criteria for selection. In addition, there are challenging issues of correctness and optimality. We present a Constraint Driven Web Service Composition tool in METEOR-S, which allows the process designers to bind Web Services to an abstract process, based on business and process constraints and generate an executable process. Our approach is to reduce much of the service composition problem to a constraint satisfaction problem. It uses a multi-phase approach for constraint analysis. This work was done as part of the METEOR-S framework, which aims to support the complete lifecycle of semantic Web processes.