Raj,
The problem with doing what you’re requesting is that MyEclipse web projects are set up in a specific directory / file structure, with some flex points, to allow our deployment tooling to operate with them seamlessly. If your external project isn’t already a MyEclipse web project it’s unlikely that it has the correct format or configuration so even if what you wanted was supported, it likely would not work as you wanted.
Another alternative would be to set up a MyEclipse web project in your workspace and copy the external artifacts to the corresponding locations in it. If you really need the source to remain where it is, you could still create the web project, to get the structure and libraries correct, and then use links to point to the various external directories from within the hierarchy of your web project. That’s a pretty advanced configuration, but it could work if your external project layout isn’t too “off” from what’s expected.
For more information on MyEclipse web projects and how they work, please see the Working with Web Projects tutorial.