Oh, then in this case you could use “LinkedAndEmbedded”, and later embed them using DestroySourceArchive()
modified = Rh.RhinoDoc.ActiveDoc.InstanceDefinitions.ModifySourceArchive(indexOfAddedBlock,Rh.FileIO.FileReference.CreateFromFullPath(location), Rh.DocObjects.InstanceDefinitionUpdateType.LinkedAndEmbedded, True)
addedBlock = Rh.RhinoDoc.ActiveDoc.InstanceDefinitions[indexOfAddedBlock]
Rh.RhinoDoc.ActiveDoc.InstanceDefinitions.DestroySourceArchive(addedBlock,True)