The need for flexible protocol stacks in communication software, instead of static, predefined protocol stacks, has been more and more asserted these last years. We present here a new environment, COMSCRIPT, which addresses the implementation of flexible protocol stacks directed by the application. COMSCRIPT is a new programming language, derived from POSTSCRIPT, which follows an interpretative approach to perform protocols. COMSCRIPT is also an interpreter, that lets execute concurrently event driven processes, whose communications occur, either synchronously or quasi-asynchronously, through synchronization points linked to gates. This paper explains these concepts and shows that the COMSCRIPT language is suited for the implementation of communication protocol entities. It also shows how the COMSCRIPT environment uses these concepts to achieve dynamic protocol stack configuration.