Practically speaking, if the numbers to be summed grow in population,
and you still want the sum to appear at the bottom, you need to put the
summation formula way down, to accomodate for the growing list of
numbers.

For example, you can place your summation at row 500.
=SUM(A1:A500)
If so, select the row where you will put the sum, and then menu Window,
and select Split. Make sure the row is the last one appearing on your
screen when you issue the command.

A simpler solution would of course be to have the sum at the top of
another column.

HTH
Kostis Vezerides