Organisations that adapt rapidly require flexible software systems. Conventional system development methods are too slow for these organisations. One way to alleviate these problems is to empower members of the organisation, domain experts, to directly control and modify such systems (user enhanceability). This paper considers the applicability of visual languages as an enabling tool for user enhanceability. Previous systems in this area have succeeded only for narrow application domains and have failed to scale up. This paper highlights some major problems in such an endeavonr, presents a generic architecture that addresses these problems and discusses a user enhanceable system for workflow applications that was implemented using this architecture.