"...keep a running total while typing?"
no, because when you're typing in a cell, you're in a different
"mode", that's why most of the toolbars get grayed out when you start
typing in a cell. Ctrl + Enter will make it so you don't move down a
cell when you hit enter. then you could always hit F2 again to edit
that cell. that's about the best I can think of. Is it super
important that you know WHILE you are typing?
dk