Gayatri,
The only way to do it is to put the reusable stuff into its own package and call it using the Execute Package Task.
DO NOT do this for eventhandlers though. The overhead of spinning up the package each time is far too much to bear. Read this: http://blogs.conchango.com/jamiethomson/archive/2005/03/01/SSIS_3A00_-A-warning-about-using-child-packages_2100_.aspx
-Jamie