I write a example follow article at 2014 SolidWorks API Help - Create Sheet Metal Costing Analysis Example (VB.NET) when get costing manager

swCosting = swModelDocExt.GetCostingManager

i get an exception:

 Unable to cast COM object of type 'System.__ComObject' to interface type 'SolidWorks.Interop.sldcostingapi.CostManager'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{BED209A9-76D4-44A1-A8AE-C5D5C0A15FF2}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE))

how can i resolve that? thanks so much.