Engine.GetWatchExpressionsChangeCount
Returns the number of modifications that have been made to the watch expression list that the engine maintains or to the watch expressions in the list.
When a WatchExpression object is inserted or removed from the watch expression list that the engine maintains or when a watch expression in the list is modified, the engine increments the change count. The sequence editor and user interfaces can use this count to determine when to refresh the watch expression pane.