pythonaddins.GetSelectedTOCLayerOrDataFrame() is too limited. Returns "none" if nothing or more than one layer is selected. It wolud be very nice if it returned a list of items and them we can test if it is a layer object or dataframe object or an empty list. It wolud be much more usable than it is now. so if i want to execute something for say five selcetde layers now the user would have to unselect and run the butten (in my case) 5 times changing tho selection between. If it returned a list it colud all be done at once. ESRI support said there is no wayto get all selected layers form the toc with a python addin at this time.