Auto Calc

If I have a workbook with the macro code below, is there any circumstance where a user on a PC or an Apple computer would NOT have the formulae auto calculate after they make changes to input (short of manually changing the calculation method to manual themselves after they open the model)?

Thanks for your help.
RR
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Private Sub Workbook_Open()

Application.ScreenUpdating = False

Application.Calculation = xlCalculationAutomatic

Application.ScreenUpdating = True
Sheets("Input").Select
Range("A1").Select

End Sub