function updateFlag() {
  // update the "required" flag adjacent to an <input> or <textrea>
  this.nextSibling.style.color = this.value ? "#898E79" : "#A03333";
};

bindings.add("input.required,textarea.required", {
  ondocumentready: updateFlag,    
  ondocumentmouseup: updateFlag,    
  ondocumentkeyup: updateFlag
});