Electronic data interchange (EDI) systems are used in many domains to support inter-organisational information exchange. To get systems using different EDI message formats to communicate, complex message translations (where data must be transformed from one EDI message format into another), are required. We describe a visual language and support environment which greatly simplify the task of the systems integrator by using a domain-specific visual language to express data formats and format translations. Complex message translations are automated by an underlying transformation engine. We describe the motivation for this system, its key visual language and transformation engine features, a prototype environment, and experience translating it into a commercial product.