Breakpoint in Flex SDK source code

[harvardFlex]

Using Flex Builder, is it possible to set a breakpoint in the Flex SDK source code? I can set a break point in my code and then step down into the SDK source, but there doesn't seem to be a way to set the breakpoint in the SDK code (The breakpoint column disappears in the source editor). I'm trying to see what's going on when the default Tree dragDrop handler is called.

Thanks!

[harvardFlex]

Figured this one out.

Right click on your Flex project directory, select properties.
Click on the Flex Build Path menu item.
Add the Flex SDK source folder to the source path.
Click OK.