Here is one method to do as you wish. The following example assumes that you wish to sum the cells A1:A9 and return the total in cell A10.
Copy the following event handler to the clipboard (highlight the entire event handler, right click inside the highlighted area, and 'Copy'):
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Column = 1 Then
Application.EnableEvents = False
For i = 1 To 10
If Cells(i, "A").HasFormula Then
Cells(i, "A").Value = ""
End If
Next
Range("A10").Formula = "=Sum(A1:A9)"
Application.EnableEvents = True
End If
End Sub
Select any worksheet and right click the sheet tab at the bottom.
Select 'View Code'.
Paste the event handler into the white editing area to the right (right click inside the area and 'Paste').
Close the VBE (red button w/white 'x' - top right).
Make numeric entries in cells A1:A9 and the sum will be returned in A10.
Delete any row 1-9.
The total will still be returned in cell A10, however there will now be a blank cell in A9. Delete any other row and the total will still be returned in cell A10, but A8 and A9 will be blank. Enter values in A8 and/or A9 and the total in A10 will be adjusted.
Note: since you wish to have a 'fixed' range of rows, you cannot insert a row as that would modify your original 'fixed' range of rows.