Model Triggers are accessed from the Toolbox. (View menu > Toolbox > Add > Modeling Logic > Model Triggers).
Model triggers allow you to execute code at different points between model runs. The following triggers are available:
On Model Open - This trigger is fired when the model is opened from the file.
On Reset - This trigger is fired when the model is reset.
On Run Start - This trigger is fired whenever the model changes from a stopped or paused state to a running state.
On Run Stop - This trigger is fired whenever the model changes from a running state to a stopped or paused state.
On Post-Compile - This trigger is fired after the completion of a compile (see Build menu and When to Compile).
For more available triggers, see the triggers section of the Model Libraries Node page.