If you want a specific workbook to open with calculation set to manual, create this sub in the workbook:

Sub Auto_Open()
Application.Calculation = xlManual
End Sub



It automatically runs when you open the workbook, and sets calculation to manual.

If you want excel to always open with calculation turned off, create personal.xlsb, save it in the correct folder and put the sub in it. You can look up how to setup and use personal.xlsb on the web. I'm not sure why you would set calculation to manual as the default, though.