Running total and copy

[Stockwell43]

Hello,

I have three field on my form I would like to total into a fourth field.
Example:

I would like to Sum: Exceptions, Before3 and After3 and place the sum in a
field called Next Day Carry Over or NDCO. Then, I would like for the total in
the NDCO field to prefill in the CarryOver field on the next record with a
click of a copy button.

Is this even do-able? At the very least, I would settle for the running sum
and the user can place the sum in the CarryOver on the next record manually.

Any help would be most appreciated!

Thanks!!