function getEvent(event){
  var evt = null;
  if (window.event){
     //IE
     evt = window.event;
  }else{
     //Firefox
    if (event){
       evt = event;
    }
  }
  return evt;
}

function getEventSourceElement(event){
  var evt = getEvent(event);
  if (evt==null){
     return null;
  }
  var element;
  if (evt.srcElement!=null){
     //IE
    element = evt.srcElement;
  }else{
     //Firefox
    element = evt.target;
  }
  return element;
}

function getElementByEvent(event,name){
  var curElement = getEventSourceElement(event);
  if (curElement==null){
     return null;
  }
  return curElement.form.elements[name];
}