Designing software that supports collaboration among multiple users in mobile ad hoc networks is challenging due to the dynamic network topology and inherent unpredictability of the environment. However, as we increasingly migrate to using mobile computing platforms, there is a pertinent need for software that can support a wide range of collaborative activities anywhere and at any time without relying on any external infrastructure. In this paper, we adopt the workflow model to represent the structure of an activity that involves multiple tasks being performed in a structured, collaborative fashion by multiple users. Using the workflow model as a base, we developed an XML based specification language called CiAN that can be used to build workflows that can be fragmented and distributed across the hosts of participating users so that the collaborative activity is executed in a distributed manner. The tasks specified in the CiAN language are executed by our Java based CiAN middleware, which runs on mobile hosts. Communication of task results between hosts occurs via a novel protocol that uses the workflow structure to make routing decisions on data packets. Complete implementation details and an evaluation of our approach are also presented