This paper describes a set of extensions (primitives, bindings and graphical modules) and their implementation to facilitate the visual assembly of web services from scientific workflows within the GridNexus computing environment. The implementation approach for this work involved employing a strategy for defining WSDL message types and procedures such that each will be bound to a defined workflow for evaluation. Because of its Axis2 foundation, web services produced by GridNexus can run under any J2EE application container by providing the service as a deployable archive file. The paper concludes with a discussion of various design alternatives including the advantages and disadvantages of each.