Вопрос решен. Спасибо Андрей VG за заданное направление. Не даром говорят: "если долго мучаться, что-нибудь получится". Для тех кто не знает, весь код хранится в модуле книги. Файл пример на основе файла Андрей VG.
Код
Option Explicit
Private WithEvents MyExcel As Application
Private FRibbon As IRibbonUI
Public Sub onGetEnabled(control As IRibbonControl, ByRef enabled)
enabled = Not MyExcel.Workbooks.Count = 0
End Sub
Public Sub setupReference(ribbon As IRibbonUI)
Set FRibbon = ribbon
End Sub
Private Sub MyExcel_NewWorkbook(ByVal Wb As Workbook)
If Not FRibbon Is Nothing Then FRibbon.Invalidate
End Sub
Private Sub MyExcel_WorkbookBeforeClose(ByVal Wb As Workbook, Cancel As Boolean)
If Not FRibbon Is Nothing Then FRibbon.Invalidate
End Sub
Private Sub MyExcel_WorkbookOpen(ByVal Wb As Workbook)
If Not FRibbon Is Nothing Then FRibbon.Invalidate
End Sub
Private Sub Workbook_Open()
Set MyExcel = Application
If Not FRibbon Is Nothing Then FRibbon.Invalidate
End Sub