How to reference a child GUI within a parent?

I know this is probably really simple, but I'm not sure how to reference a GUI that is the child of another GUI.

For example, I have this GUI structure:

menuGUI
---itemGUI
------iconGUI
------nameGUI
------priceGUI

I'm trying to figure out how to change the value for the nameGUI from the default value, "unnamed", to "fred".

This was my attempt to code this:

%this.obj = menGUI;
%this.obj.itemGUI.nameGUI = "fred";

Anyone know what I've done wrong?