Accessing function located in the loading movie

I really need help on this one. I have a function to resize my stage which is located in the main movie. There is another movie which is loaded into the main movie and I want the loading movie to call the resize function which is located into the main movie. In short how can I access functions which are located on the main loading movie.

I have treid _level0.resize(); // Doesn’t work
_level.parent.resize(); // Doesn’t work

But at the same time there is a text field which I can easily update throught the loaded movie by

_level.my_text.text = “Anything”; // Does work

I have spent my whole night on this but can’t find anything on it.