How do you create a jquery plugin that needs to keep state?

toggle_field_on_select_value.js

  $.fn.toggle_field_on_select_value = function(select_input, value) {
    toggle = function (){
      $select = $(select_input);
      $this = $(this);
      if($select.attr("value") == value){
        $this.slideDown();
      }else{
        $this.slideUp();
      }
    }
    toggle();
    $this.change(toggle);
  }