I want to display the current setting of Tools / Options / Calculation
("Manual" or "Automatic" or "Automatic except tables") in a cell of my
workbook.

Question 1:
The following UDF does half-work: it displays correctly when I switch from
Manual to Automatic but not the other way round. What's wrong?

Function Get_Calc(Sheet As String) As Long
With Application
Get_Calc = .Calculation
End With
End Function

Question 2:
Only by trying have I found the following results from my UDF - is that
correct? where can I find a comprehensive overview of these value/setting
correlations?
-4135 = Manual
-4105 = Automatic
2 = Semi Automatic