How to select suboccurrence via API ?

When i run this code

SolidEdgeFramework.SelectSet SS=Application.ActiveSelectSet;
SS.Add(Occ); //Occ is SolidEdgeAssembly.Occurrence object
SS.Add(SubOcc); //SubOcc is SolidEdgeAssembly.Suboccurrence object

i get result:

Occ is selected.
SubOcc is not selected.

Thanks.

Alredy I know, how to select suboccurrence. Suboccurrence is not selectable, but reference is selectable. I create reference from suboccurrence and select it with SelectSet.Add(Reference). Here is example in C#:

SolidEdgeAssembly.AssemblyDocument A=SubOcc.TopLevelDocument;
SolidEdgeAssembly.Occurrence O=(SolidEdgeAssembly.Occurrence)SubOcc.Parent;
SolidEdgeFramework.Reference R=(SolidEdgeFramework.Reference)A.CreateReference(O,SubOcc.ThisAsOccurrence);

Alredy I know, how to select suboccurrence. Suboccurrence is not selectable, but reference is selectable. I create reference from suboccurrence and select it with SelectSet.Add(Reference). Here is example in C#:

SolidEdgeAssembly.AssemblyDocument A=SubOcc.TopLevelDocument;
SolidEdgeAssembly.Occurrence O=(SolidEdgeAssembly.Occurrence)SubOcc.Parent;
SolidEdgeFramework.Reference R=(SolidEdgeFramework.Reference)A.CreateReference(O,SubOcc.ThisAsOccurrence);