Application developers utilizing event-based middleware have sought to leverage domain-specific modeling for the advantages of intuitive specification, code synthesis, and support for design evolution, among other benefits. For cyber-physical systems, the use of event-based middleware may result, for some applications, in a need for additional time-based blocks that were not initially considered during system design. An advantage of domain-specific modeling is the ability to refactor an application to include time-triggered, event-based schedulers. In this paper we present an application in need of such modification, and discuss how these additional blocks must be synthesized in order to conform to the input/output constraints of the existing diagram. Categories and Subject Descriptors D.2.6 [Software Engineering]: Prog. Environments—Integrated environments Keywords Metamodeling, software synthesis, graph rewriting