See:
http://stackoverflow.com/questions/33868125/cannot-enable-remove-data-from-the-external-data-range-before-saving-the-workbo/33886877#comment55538909_33886877
http://stackoverflow.com/questions/33868125/cannot-enable-remove-data-from-the-external-data-range-before-saving-the-workbo/33886877#comment55538909_33886877
