Thank you for you're reply...and question re what I'm trying. The object within an object is a proxy for a combo box that I've made i.e. the list box is in the parent object and the child object is a TK entry widget that I've "enhanced" and that is useful in it's own right. The combo boxes will be used in clusters and whilst there's some similarity in their functionality (locked away in the objects) I wanted to customise them by passing in a non-oop subroutine that gets called when a key is pressed in the entry (child object). To this end I'm passing the non-oop customising subroutine into the parent object to pass onto the child object upon it's creation along with a reference to the parent object. This is so the child object (entry) can call the custom subroutine and supply it with the parent object's reference when the entry's custom bindtag fires. I could reference the combo's directly 'cos they created in main just like the non-oop sub but wonder how you'd pass a combo reference internally...for future reference i.e. I can get around this but in a not very oop-way. Hope that explains