This paper proposes a web-based interactive workflow definition and invocation system assisting users in orchestrating a set of distributed services-activities and expressing complex dependencies between them in XML. We use Ant, which is a Java-based and freely distributed commodity tool, for workflow definitions and workflow engine. Adopting Ant as a workflow engine provides platform independence and immediate integration into the Grid services framework. Sometimes, workflow scripts need to be used repeatedly with a little change; framework enables reusable scripts to be created, stored and edited for later use. This allows sharing and dynamic modifications of workflows between multiple participants. The practicality and usefulness of the system is demonstrated through a concrete case study on Remote Method Invocation (RMI) jobs. Copyright (c) 2014 John Wiley & Sons, Ltd.