The extent of coupling in an object-oriented system has implications for its quality in terms of software maintenance. In turn, the extent of reuse in a software system also has implications for the maintainability of that system. One important feature of reflective systems is their dynamic behaviour. In such systems, objects exchange coupling interactions to a larger degree than corresponding static systems providing the same functionality. In this paper, we look at object coupling as it evolves during program execution and propose a measure which takes object interactions into account. The measure can be used to compare systems built on meta-level architectures with systems having no reflective features yet, at the same time, exhibiting the same interface.