Implementation of behavior within graphical DSL

Question

I started writing graphic dsl in eclipse by using Epsilon. However the problem is there is that epsilon doesn't have support for writing specific behavior for dsls. For the reference, i'm writing a dsl for data flow diagrams, where i'd need to implement system for decomposition, meaning i'd have to fetch all of external entities, interfaces and connections that are related to the process i'm decomposing it by and transfer them to lower level of decomposition. Does anyone know if there's a way to deal with this problem within epsilon framework, or is there any other framework that would allow me to make dsl out of metamodel with addition of defining a behavior for the dsl.