HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\11.0\Registration\{90110407-6000-1_
  1D3-8CFE-0150048383C9}\DigitalProductID
und 
 
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\11.0\Registration\{90110407-6000-1_
  1D3-8CFE-0150048383C9}\ProductID

Try
            Dim o As Object = CreateObject("outlook.Application")
            Dim version As String = o.version
            TextBox2.Text = o.version
        Catch ex As Exception
        End Try