My file is loaded with custom functions and therefore recalculates
very slowly. To make it easier to work with the file I set it to
"manual" calculations.
However, I have a problem when opening the file - it immediately
starts recalculating and it takes forever for the file to open. The
only solution is to set options to manual calculation before opening
the file. I tried to automate this by writing a code under
"ThisWorkbook" object:

Private Sub Workbook_Open()

Application.Calculation = xlCalculationManual

End Sub

Unfortunately, it didn't solve the problem. This code doesn't seem to
be working - the file still recalculates when I open it. Is there a
way to automate this and set options to manual calculation when
opening the file, but before it starts recalculating everything?

Thank you for your help.

German.