ActionScripting Basics: One-Click Adding and Removing Scripts
From Adrien-Luc Sanders, former About.com Guide
You can add to your Flash Actionscripts any number of ways, but one of the easiest ways is to use the little + and buttons above the window that displays the actual code. As expected, the + button will let you add a script, while the button lets you delete one.
Flash Animation Tutorials: Step-by-Step Lessons