Domain specific languages (DSLs) play a cornerstone Model-Driven Software Development. The abstract syntax of a DSL is usually defined by a metamodel, while inplace model transformation rules provide an intuitive way to complement metamodels with their behavioral specifications. We propose a modeling notation that extends in-place rules with a quantitative model of time, and with mechanisms that allow designers to specify action-based properties, thus facilitating the design of real-time complex systems. We present a graphical modeling tool that we have built for visually specifying these timed behavioral specifications.