Variable Check Rule
From TrainzOnline
The Variable Check Rule is used to execute custom rules based on the value of a session variable. For information on how to define and modify a session variable, see the Variable Modify Rule. The rule can be configured to test the variable value once upon execution, or once every second. Single tests are more efficient, and are recommended, but they are not always possible. If the test passes the variable check rule will then execute each of it's child rules in sequence.