Private Sub Workbook_Open()
    Application.EnableEvents = False
    MsgBox ("Workbook_Open")
End Sub

Private Sub auto_open()
    Application.EnableEvents = False
    MsgBox ("auto_open")
End Sub

Private sub auto_open()
    For Each WB In Workbooks
       If WB.Name <> ThisWorkbook.Name Then
           WB.Close
       End If
   Next
end sub

Private sub auto_open()
    For Each WB In Workbooks
       If WB.Name <> ThisWorkbook.Name Then
           WB.Close
       End If
   Next
end sub

Private Sub Workbook_Open()
    Dim sourceWB As Workbook
    Do While sourceWB Is Nothing
        Set sourceWB = ThisWorkbook
        DoEvents
    Loop
End Sub

Sub Workbook_open()
    Dim sourceWB As Workbook
    Do While sourceWB Is Nothing
        Set sourceWB = ThisWorkbook
        DoEvents
    Loop
End Sub

Private Sub Workbook_Open()
    For Each WB In Workbooks
        If WB.Name <> ThisWorkbook.Name Then
            WB.Close &#39; SaveChanges:=False
        End If
    Next
End Sub

Private Sub UserForm_Initialize()
    ...
    Application.Visible = False
    ...    
End Sub

Private Sub UserForm_Terminate()
    ...
    Application.Visible = True
    ...
End Sub