Peter, Sorry I can't be of much help, but I share the same interest as you. There may be some teaser info here although I can't claim to understand the technique. http://www.java2s.com/Open-Source/Python/3.1.2-Python/Demo/Demo/tkinter/ttk/notebook_closebtn.py.htm If you have any links/documentation to share, I would love to see what you've found so far. Malcolm