[bes]

<div id="myDiv">
  <input>
  <input type="button" value="red">
  <input type="button" value="green">
</div>


<script>
window.onload = function () {
  var myDiv = document.getElementById('myDiv');
  var inputs = myDiv.getElementsByTagName('input');

  myDiv.onclick = function (e) {
    e = e || window.event;
    var target = e.target || e.srcElement;

    if (target.parentNode == myDiv && target != inputs[0]) {
      inputs[0].value += target.value + ', ';
    }

  }

}
</script>