need formula with a temp variable - excel

Question

we have all added information in our heads and then written the results down,
for example a simple tally, yesterday I sold 10 apples, the day before I sold 5 for a total of 15, today I sold 5 for a total of 20, a simple equation we all do every day in our head without even thinking about it, the formula I believe would basically read: A+B=Bnew
where A would be the daily sale.
B would be the total sale
and Bnew is the new total.
how do I do this in excel without taking pages of running total lines, or fancy visual basic script.
I want to use at most 3 cell's
Cell-1 = changing variable, (the daily sale)
Cell-2 = the running total of all sales to which A1 will be added.
and if needed Cell-3 to hold the contents of Cell-2 like our memory holds it while we update the total.
a very simple math problem, but driving me nuts to try to get excel to do it, I have searched and searched but I don't even know the right question to ask.
thank you for your help

Answer 1

Given the restrictions:
No helper columns ("without taking pages of running total lines")
No VBA ("no fancy visual basic script")
"I want to use at most 3 cell's"
I think a remaining option is iterative calculation? I don't know, maybe someone else can think of a better solution. But regarding iterative calculation, here's how I've set my sheet up:
This uses two cells (ignoring the labels in row 1):
In cell A2, I have the formula =A2+B2
Cell B2 is blank (ready to have some number entered)
I then go to File > Options > Formulas > Enable iterative calculation > Change "Maximum Iterations" to 1 > OK
Any notifications regarding circular references should now disappear, and if I put a number in cell B2, cell A2 updates in the manner you described in your post. Hopefully, you can replicate this on your machine too.
The thing to note is the iterative calculation setting you'll change is application-wide, so I believe it affects all other workbooks. Something to keep in mind.

Answer 2

If your setup looks like this in Sheet1:
then a small vba macro in the worksheetmodule from Sheet1 should do the trick:
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Address = "$A$2" Then
Range("B2").Value = Range("B2").Value + Range("A2").Value
End If
End Sub
This subroutine will run after every worksheet change. It will check if the change was in cell A2. If that's the case the value in A2 will be added to the value in B2.

Answer 3

Assuming you're okay with a small amount of VBA code, you could try putting the code below into the worksheet module for the sheet where you're entering the data:
Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
' Assumes "daily sales" are entered into cell B2 and that "running total" is in cell A2
If Not (Intersect(Target, Me.Range("B2")) Is Nothing) Then
Me.Range("A2").Value2 = Application.Sum(Me.Range("A2").Value2, Target.Value2)
End If
End Sub
(Pressing Alt + F11 concurrently should open the editor, you can then find worksheet modules on the left).
If you then enter a number in cell B2, then cell A2 should update in a cumulative manner. If you enter a number in a cell other than B2 or A2, you should find cell A2 doesn't update (unlike the iterative calculation approach). We use Application.Sum instead of + operator to avoid Type Mismatch error, if either A2 or B2 contain non-numeric data.
Try it, see if it does what you're after.
Edit:
If you have multiple rows, you could try something like below.
Private Sub Worksheet_Change(ByVal Target As Range)
' Assumes "daily sales" are entered into column B and that "running total" is in column A
If Target.Column = 2 Then
Me.Cells(Target.Row, "A").Value2 = Application.Sum(Me.Cells(Target.Row, "A"), Target)
End If
End Sub