All surfaces in a drawing are located in the AeccDocument.Surfaces collection. Each surface in the collection can be accessed through the AeccSurfaces.Item method, which takes either an integer index or the string name of the surface. The AeccSurfaces.Item method returns a generic reference of type AeccSurface, so you need to check the AeccSurface.Type property to actually determine what kind of surface it is.
This sample examines each surface in the drawing and reports what kind of surface it is:
Dim oSurface As AeccSurface Dim i As Integer For i = 0 To oAeccDocument.Surfaces.Count - 1 Set oSurface = oAeccDocument.Surfaces.Item(i) Select Case (oSurface.Type) Case aecckGridSurface: Dim oGridSurface As AeccGridSurface Set oGridSurface = oSurface Debug.Print oGridSurface.Name & ": Grid" Case aecckTinSurface: Dim oTinSurface As AeccTinSurface Set oTinSurface = oSurface Debug.Print oTinSurface.Name & ": TIN" Case aecckGridVolumeSurface: Dim oGridVolume As AeccGridVolumeSurface Set oGridVolume = oSurface Debug.Print oGridVolume.Name & ": Grid Volume" Case aecckTinVolumeSurface: Dim oTinVolume As AeccTinVolumeSurface Set oTinVolume = oSurface Debug.Print oTinVolume.Name & ": TIN Valume" End Select Next i