There is a VBA solution for 2004 and prior, but it does not work in 2005+ perhaps someone else could look at it and get a different view...
Dim PaperWidthList(10000) As Double
Dim PaperHeightList(10000) As Double
Dim MediaNameList(10000) As String
Dim plotDevicesList(10000) As String
Dim i As Integer
Sub AcadDocument_ObjectModified(ByVal Object As Object)
On Error Resume Next
If TypeName(Object) = "IAcadLayout" Then
i = i + 1
ThisDrawing.ActiveLayout.RefreshPlotDeviceInfo
MediaNameList(i) = ThisDrawing.ActiveLayout.CanonicalMediaName
plotDevicesList(i) = ThisDrawing.ActiveLayout.ConfigName
ThisDrawing.ActiveLayout.GetPaperSize PaperWidthList(i), PaperHeightList(i)
End If
End Sub