dropdownlist menu แบบ 2 ชั้น ระดับสองข้อมูลหายค่ะ

<?php
mysql_select_db($database_Conn, $Conn);
$query_RecordsetDegree = "SELECT * FROM degree";
$RecordsetDegree = mysql_query($query_RecordsetDegree, $Conn) or die(mysql_error());
$row_RecordsetDegree = mysql_fetch_assoc($RecordsetDegree);
$totalRows_RecordsetDegree = mysql_num_rows($RecordsetDegree);

mysql_select_db($database_Conn, $Conn);
$query_RecordsetRoom = "SELECT * FROM room";
$RecordsetRoom = mysql_query($query_RecordsetRoom, $Conn) or die(mysql_error());
$row_RecordsetRoom = mysql_fetch_assoc($RecordsetRoom);
$totalRows_RecordsetRoom = mysql_num_rows($RecordsetRoom);
?>

<script language = "JavaScript">
		function ListRoom(SelectValue)
		{
			form1.RoomID.length = 0

			//*** Insert null Default Value ***//
			var myOption = new Option('','')  
			form1.RoomID.options[form1.RoomID.length]= myOption
			
			<?php
			$intRows = 0;
			
			
			while ($row_RecordsetRoom = mysql_fetch_assoc($RecordsetRoom))
			{
			$intRows++;
			?>
				x = <?php echo $intRows; ?>;
				mySubList = new Array();
				
				strGroup = <?php echo $row_RecordsetRoom['DegreeID']; ?>;
				strValue = "<?php echo $row_RecordsetRoom['RoomID']; ?>";
				strItem = "<?php echo $row_RecordsetRoom['RoomName']; ?>";
				mySubList[x,0] = strItem;
				mySubList[x,1] = strGroup;
				mySubList[x,2] = strValue;
							
				if (mySubList[x,1] == SelectValue){
					var myOption = new Option(mySubList[x,0], mySubList[x,2])  
					form1.RoomID.options[form1.RoomID.length]= myOption					
				}
			<?php
			}
			?>																	
		}

</script>


<table>
 <tr valign="baseline">
           <td nowrap="nowrap" align="right">ระดับชั้น:</td>
           <td><select name="DegreeID" onChange="ListRoom(this.value)">
           <option selected value=""></option>
             <?php
do {  
?>
             <option value="<?php echo $row_RecordsetDegree['DegreeID']?>"><?php echo $row_RecordsetDegree['DegreeName']?></option>
             <?php
} while ($row_RecordsetDegree = mysql_fetch_assoc($RecordsetDegree));
  $rows = mysql_num_rows($RecordsetDegree);
  if($rows > 0) {
      mysql_data_seek($RecordsetDegree, 0);
	  $row_RecordsetDegree = mysql_fetch_assoc($RecordsetDegree);
  }
?>
           </select></td>
         </tr>
         <tr valign="baseline">
           <td nowrap="nowrap" align="right">ห้องเรียน:</td>
           <td><select name="RoomID" id="RoomID"></select></td>
         </tr>
</table>