public void SetDefinition( 
   CIMMapSeries cimMapSeries
)

//Get and modify a map series CIM definition and set the changes back to the layout

//Perform on the worker thread
await QueuedTask.Run(() =>
{
  MapSeries MS = layout.MapSeries as MapSeries;
  CIMMapSeries CIM_MS = MS.GetDefinition();
  CIM_MS.Enabled = false;
  MS.SetDefinition(CIM_MS);
  layout.SetMapSeries(MS);
});