I have somethinng like below, and wanted to make sure from date shall not overpass to date which is not selectable(even after changing the date) and vice versa.
From: <input type="text" id="xx_from" value="<?php echo $date_from; ?>" /> 
To: <input type="text" id="xx_to" value="<?php echo $date_to; ?>" />
$j("#xx_from").datepicker({
      dateFormat: 'yy-mm-dd',
      maxDate: $j("#xx_to").val(),
      onSelect: function(){
        $j("#xx_to").datepicker( "refresh" );
      }
  });
  $j("#xx_to").datepicker({
      dateFormat: 'yy-mm-dd',
      minDate: $j("#xx_from").val(),
      onSelect: function(){
        $j("#xx_from").datepicker( "refresh" );
      }
  });
 
     
     
    