Class problem

Hi there,
I am creating a site for the first time in AS3 and I'm using external classes. I have a main document class and then for a number of other sections I have classes linked to their respective container movieClips. If I want to access something on the stage from a class linked to a specific movieclip how would I do it ? For example I have a portfolio class linked to my portfolio container clip which is in the following location: root.mainContainer.sectionsContainer.portfolioContainer. I want to be able to control the position of "mainContainer" from my portfolio class. Is that possible ?

thanks,
k