Just some JS about destroying and stuff

some.js

// somewhere else in time and space
SomeView = new Backbone.Marionette.View.extend({
  
  onDestroy: function(){
    App.vent.trigger('define:var:to:block:callback');
  }

});

// some other view
MyView = new Backbone.Marionette.View.extend({
    initialize: function(){
      this.listenTo(App.vent, 'define:var:to:block:callback', this.defineVar);
    },
   defineVar: function(){
    this.stopWhatYouAreAboutToDo = true
   }
});