[AS2/CS4] function trouble!

hello everyone!
i’m having an issue calling a function from a movieclip.
I have a button that creates a variable and then sends that variable to the root timeline.
I think that the issue is that the function is looking for the “item” variable on the root timeline.
here is the code:

var item = new CartItem

//description, cost, qty
(DESC, 100.00, 1);

when I have this button on the main timeline everything works alright, though when its in a movieclip it returns “undefined” This is all apart of a shopping cart i’m working on.

does anybody have any thoughts or suggestions? I would really appreciate any help I can get. Many thanks in advance!