‘Returns a count of all workbooks with at least
    ‘one visible window.  Takes no arguments.
    
    Dim oWb As Workbook
    Dim oWin As Window
    Dim lVisible As Long
    
    ‘Loop through workbooks
    For Each oWb In Application.Workbooks
        ‘Loop through windows for each wb
        For Each oWin In oWb.Windows
            ‘Increment counter and stop processing
            ‘windows for this workbook
            If oWin.Visible Then
                lVisible = lVisible + 1
                Exit For
            End If
        Next oWin
    Next oWb
    
    VisibleWbCount = lVisible
    
End Function

Function VisibleWbCount2()

    Dim oWin As Window
    Dim cBooks As Collection
    
    ‘Create collection to store unique
    ‘workbook names
    Set cBooks = New Collection

    ‘Loop though windows and add workbook name to
    ‘collection
    For Each oWin In Application.Windows
        On Error Resume Next
            cBooks.Add oWin.Parent.Name, CStr(oWin.Parent.Name)
        On Error GoTo 0
    Next oWin
    
    VisibleWbCount2 = cBooks.Count
    
End Function