See
  http://word.mvps.org/faqs/tblsfldsfms/SetTabOrder.htm

But it is not an altogether easy solution to implement or to use (as a user
working with the form)...

Have you protected the form? If so, you should be able to tab from one form
field to another. If the "input fields" are not form fields (if, for
example, they're MacroButton fields), you can use F11 instead.