Try using those macros to switch between Auto & Manual Calculation.

Sub Calcul_Manual()
Application.Calculation = xlManual
End Sub

Sub Calcul_Auto()
Application.Calculation = xlAutomatic
End Sub

I'd recommend putting two macro buttons in your worksheet.

And this procedure will switch to Manual when the file is closed:

Sub Auto_Close
Calcul_Manual
End Sub

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Tomek Polak, http://vba.blog.onet.pl