How do I resize a symbol instance from within itself?

I am dynamically adding symbol instances to create a menu from json data. I want the menu item height to expand during mouse over.

So I want to animate the height of the symbol from within itself, but the root div element is read only.

My solution is to animate a rectangle, then copy its height to its parents height, which once the symbol is instanced should be a normal editable div.

My timeline update function in the symbol looks like this:

sym.$("HeightRect").parent().height( sym.$("HeightRect").height() );

But it doesn't work. sym.$("HeightRect").parent() doesn't seem to return the instance of the symbol.

Any ideas?