Thanks for your reply,
I think I found out what I was doing wrong in FlashDevelop.
It's very basic, but I couldn't find it anywhere so hopefully it'll help others.
If you are getting : Type was not found or was not a compile-time constant
In my case, I had copied the com/greensock... folders in my AS3 project folder. I then added them in the classpath. Everything seems to work until you compile. BUT, you need to move the "com" folder into a subfolder called "greensock".
So you'll have:
And add it to your classpath.
This worked for me.