iam using form to add new target to user
i need when he choose from menu without refresh page the information about this record show in text (chained select)
i'm using ajax but code have error i don't know it
code for part_a_new

HTML Code:
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Part A</title>
<style type="text/css">
body {
	background-image: url(images/background.png);
}
</style>
<script type="text/javascript" language="javascript" src="css/jquery2.js"></script>

<script language="javascript" type="text/javascript">
function getXMLHTTP() { //fuction to return the xml http object
		var xmlhttp=false;	
		try{
			xmlhttp=new XMLHttpRequest();
		}
		catch(e)	{		
			try{			
				xmlhttp= new ActiveXObject("Microsoft.XMLHTTP");
			}
			catch(e){
				try{
				xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
				}
				catch(e1){
					xmlhttp=false;
				}
			}
		}
		 	
		return xmlhttp;
    }
	
	function getMake(id) {		
		
		var strURL="findmake.php?id="+id;
		var req = getXMLHTTP();
		
		if (req) {
			
			req.onreadymakechange = function() {
				if (req.readyMake == 4) {
					// only if "OK"
					if (req.status == 200) {						
						document.getElementById('makediv').innerHTML=req.responseText;						
					} else {
						alert("There was a problem while using XMLHTTP:\n" + req.statusText);
					}
				}				
			}			
			req.open("GET", strURL, true);
			req.send(null);
		}		
	}
	function getMake(id) {		
		var strURL="findlast.php?id="+id;
		var req = getXMLHTTP();
		
		if (req) {
			
			req.onreadymakechange = function() {
				if (req.readyState == 4) {
					// only if "OK"
					if (req.status == 200) {						
						document.getElementById('lastdiv').innerHTML=req.responseText;						
					} else {
						alert("There was a problem while using XMLHTTP:\n" + req.statusText);
					}
				}				
			}			
			req.open("GET", strURL, true);
			req.send(null);
		}
				
	}
</script>
</head>
<body>
<form action="<?php echo $editFormAction; ?>" method="post" name="form1" id="form1">
 <table align="center">
<td nowrap="nowrap" align="right">Substation_name:</td>
      <td><select name="substation_name" onChange="getmake(this.value)">
        <?php
do {  
?>
        <option value="<?php echo $row_substation['id']?>"><?php echo $row_substation['station']?></option>
        <?php
} while ($row_substation = mysql_fetch_assoc($substation));
  $rows = mysql_num_rows($substation);
  if($rows > 0) {
      mysql_data_seek($substation, 0);
	  $row_substation = mysql_fetch_assoc($substation);
  }
?>
      </select></td>
    </tr>
    <tr> </tr>
    <tr valign="baseline">
      <td nowrap="nowrap" align="right">Make:</td>
      <td><div id="makediv"><select name="make">
        	<option> </option>
      </select></div></td>
    </tr>
    <tr> </tr>
    <tr valign="baseline">
      <td nowrap="nowrap" align="right">Prev_MTC:</td>
  <td><div id="lastdiv"><select name="last">
               	<option> </option>
      </select></div></td>
</table>
<body>
code for findmake.php
HTML Code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
</head>

<body>
<?php $make=intval($_GET['id']);
$link = mysql_connect('localhost', 'root', ''); //changet the configuration in required
if (!$link) {
    die('Could not connect: ' . mysql_error());
}
mysql_select_db('trsh');
$query="SELECT id,make FROM substations WHERE id ='$make'";
$result=mysql_query($query);

?>
<select name="make" onchange="getMake(<?php echo $make ?>,this.value)">
  <option></option>
  <?php while($row=mysql_fetch_array($result)) { ?>
  <option value><?php echo $row['make']?></option>
  <?php } ?>
</select>
</body>
</html>
code for findlast.php

HTML Code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
</head>

<body>
<?php $last=intval($_GET['id']);
$link = mysql_connect('localhost', 'root', ''); //changet the configuration in required
if (!$link) {
    die('Could not connect: ' . mysql_error());
}
mysql_select_db('trsh');
$query="SELECT id,last FROM substations WHERE id ='$last'";
$result=mysql_query($query);

?>
<select name="last" onchange="getMake(<?php echo $last ?>,this.value)">
  <option></option>
  <?php while($row=mysql_fetch_array($result)) { ?>
  <option value><?php echo $row['last']?></option>
  <?php } ?>
</select>

</body>
</html>
database
new:
id,station,make,last,foward,user,date
station:
id,station,make,last

we bring data fron station to but in new and complete information

plz help me