All surface styles are stored in the AeccDocument.SurfaceStyles collection, an object of type AeccSurfaceStyles. To create a new style, call the AeccSurfaceStyles.Add method with the name of your new style. It is initially set according to the document’s ambient settings.
Dim oSurfaceStyle As AeccSurfaceStyle
oSurfaceStyle = oDocument.SurfaceStyles.Add("New Style")