Adding value of two cells to get result in 3rd cell

[DocAElstein]

Try running this macro once, then try your macros again, there is a small chance that it might help

Sub Oops()
 Let Application.ScreenUpdating = True
 Let Application.Calculation = xlCalculationAutomatic
 Let Application.EnableEvents = True
 Let Application.DisplayAlerts = True
End Sub

Note also that your macro must be in the same workbook and in the worksheet object code module of the worksheet in which you have the data to be added.