I would like to create a running total that adds on to itself. Is there a
way I can do this...simply, lol? Thanks! Here is an example

mileage on mileage off subtotal total miles
54999 55000 1 I want this number to
add to
itself as I
change the subtotal.
*not a running total that descends down the page, I only get one line per
tire and I need to keep the total miles dynamic within one cell. I can't
figure how to make the sum add to itself.
Hopefully, I was able to explain that correctly. Thanks!