A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Excel does not control the keyboard in that regard.
Apple keyboards do not [typically] have Num Lock markings because there is a separate set of navigation keys. Most Mac users use them rather than toggling a Num Lock on/off, so the keypad usually remains in a numeric mode.
If you prefer having to toggle back & forth, use Shift+Clear... I just reconfirmed it here in OS X 10.6.8 but I'm assuming it still works in more recent releases of OS X.