Django - Access parent window in ModelAdmin

Question

Hello,

I have a class called News which have a choices field called category. Each category is also representing by classes with the News class as foreignKey field.

So in admin, when I create a new category instance, I have to create a News, which is represented with a popup.

The main page which represents the category class is the parent of the News class popup. I would like that the category choice field been selected according to the parent window.

Is there a method on load like save_model for save ? and how can access to data of the parent window?

Thanks for help