Accessing parent movie's variables

I have a file called Main.swf that used loadMovieNum to load a file
called UI.swf onto level 4.

What I want to be able to do is access variables in Main.swf, from
within UI.swf


Is that possible ?

If so, what is the syntax for say accessing a variable say on the root in
Main.swf, from within UI.swf ?

Thanks in advance for any help any of you can provide.