This paper presents AspectFX, a novel approach to enabling developers and designers to collaborate effectively in RIA development. Unlike traditional web applications, RIAs are implemented by a number of developers and designers; therefore it is reasonable to divide an application into modules and assign them to developers and designers, and collaborative works among them have been important. MVC architecture and OOP helps to divide an application into functional units as modules and bring efficiency to development processes. To play these modules as a single application, developers have to describe method invocations to utilize functionalities implemented in modules, however, developers need to describe additional method invocations that are not primary tasks for them. These additional method invocations make the dependencies among modules strong and these dependencies make it inefficient/difficult to implement and maintain an application. This paper describes the design and implementation of AspectFX that introduces aspect-oriented concept and considers the additional method invocations as cross-cutting concerns. AspectFX provides methods to separate the cross-cutting concerns from primary concerns and weaves them for playing them as an application.