The Schedule Mark parameter. On creation, the Schedule Mark is set to a value that is unique to the host, but it can be set to any value. 
   Namespace:   Autodesk.Revit.DB.Structure  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2013 
Syntax
Exceptions
| Exception | Condition | 
|---|---|
| Autodesk.Revit.Exceptions ArgumentNullException | When setting this property: A non-optional argument was NULL | 
| Autodesk.Revit.Exceptions DisabledDisciplineException | When setting this property: None of the following disciplines is enabled: Structural. |