<input  onclick="selStart(this)" value="1,22,333,2,322,6,3321"/>
<script type="text/javascript">
function selStart(o){
  if(document.selection){
    o.focus();
    var r = document.selection.createRange(),tr=o.createTextRange();
    tr.setEndPoint('endtoend',r);
    o.selectionStart=tr.text.length-r.text.length;
    o.selectionEnd=tr.text.length;
  }
  alert(o.selectionStart+'\n'+o.selectionEnd);
}
</script>