Private Sub Workbook_Open()

    Const strExceltoWiki As String = "Copy Selection to Wiki"
    
    Dim myButton As CommandBarButton
    Dim Wb As Workbook
    Dim I As Integer
    
    'Check in current Tools menu if item already exist
    For I = 1 To Application.CommandBars("Tools").Controls.Count
        If Application.CommandBars("Tools").Controls(I).Caption = strExceltoWiki Then
            Exit Sub
        End If
    Next I
    
    Set myButton = Application.CommandBars("Tools").Controls.Add(Type:=msoControlButton, temporary:=True)
    myButton.Caption = strExceltoWiki
    myButton.Style = msoButtonCaption
    myButton.BeginGroup = True
    myButton.OnAction = "SelectionToWiki"

End Sub