Does this stop only the Cancel Key or any key/mouseclick that focuses
on a cell in the workbook?

I have found that selecting a cell on any of the worksheets  while the
timer or routine  is running  may or may not interrupts the timer. I can
select another sheet and have no problem, I can scroll slowly through
a sheet with no problem. A mouse click in any cell, even an empty one,
will sometimes interrupt the timer; accidently entering something from
the keyboard  into a cell always interrupts the timer. Since I want to
work elsewhere on the desktop while the program is running, I am
looking for a way to make  the sheets impervious to any external entry.