Web service may be unable to interact with each other because of incompatibilities between their interfaces. In this paper, we present an event driven approach which aims at adapting messages exchanged during service interactions. The proposed framework relies on Complex Event Processing (CEP) technology, which provides an environment for the development of applications that need to continuously process, analyse and respond to event streams. Our main contribution is a system that enables developers to design and implement CEP-based adapters. These latter are deployed in a CEP engine which is responsible for continuously receiving messages and processing them according to rules implemented by the adapters. Resulting transformed messages are thus forwarded to their original service recipient.