ปัญหาเรื่อง Ajax Auto Fill Textbox ในการแสดงหลายTextFile

<script language="JavaScript">
	   var HttPRequest = false;

	   function doCallAjax(fProductID,fProductName,fPrice) {
		  HttPRequest = false;
		  if (window.XMLHttpRequest) { // Mozilla, Safari,...
			 HttPRequest = new XMLHttpRequest();
			 if (HttPRequest.overrideMimeType) {
				HttPRequest.overrideMimeType('text/html');
			 }
		  } else if (window.ActiveXObject) { // IE
			 try {
				HttPRequest = new ActiveXObject("Msxml2.XMLHTTP");
			 } catch (e) {
				try {
				   HttPRequest = new ActiveXObject("Microsoft.XMLHTTP");
				} catch (e) {}
			 }
		  } 
		  
		  if (!HttPRequest) {
			 alert('Cannot create XMLHTTP instance');
			 return false;
		  }

		  var url = 'AjaxGetFill.php';
		  var pmeters = "tProductID=" + encodeURI( document.getElementById(fProductID).value);

			HttPRequest.open('POST',url,true);

			HttPRequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
			HttPRequest.setRequestHeader("Content-length", pmeters.length);
			HttPRequest.setRequestHeader("Connection", "close");
			HttPRequest.send(pmeters);
			
			
			HttPRequest.onreadystatechange = function()
			{

				//if(HttPRequest.readyState == 3)  // Loading Request
				//{
					//document.getElementById(fProductName).innerHTML = "..";
				//}

				if(HttPRequest.readyState == 4) // Return Request
				{
					var myProduct = HttPRequest.responseText;
					if(myProduct != "")
					{
						var myArr = myProduct.split("|");
						document.getElementById(fProductName).value = myArr[0];
						document.getElementById(fPrice).value = myArr[1];
					}
				}
				
			}

	   }
	</script>


<form name="frmMain">
<table width="70%" border="1">
  <tr>
    <th width="84">Product ID </th>
    <th width="185">Product Name </th>
    <th width="99">Price</th>
    <th width="99">&nbsp;</th>
    <th width="99">&nbsp;</th>
  </tr>
  <tr>
    <th>
      <div align="center">
        <input type="text" name="txtProductID1" id="txtProductID1" OnChange="JavaScript:doCallAjax('txtProductID1','txtProductName1','txtPrice1','textfield','textfield2');">
      </div></th>
    <th><input type="text" name="txtProductName1" id="txtProductName1" size="30"></th>
    <th><input type="text" name="txtPrice1" id="txtPrice1" size="10"></th>
    <th><input type="text" name="textfield" id="textfield"></th>
	<th><input type="text" name="textfield2" id="textfield2"></th>
    </label></th>
  </tr>
  <tr>
    <th>
      <div align="center">

<?php
	/*** By Weerachai Nukitram ***/
	/***  http://www.ThaiCreate.Com ***/

	$strProduct = trim($_POST["tProductID"]);


	$objConnect = mysql_connect("localhost","library","compaq") or die("Error Connect to Database");
	$objDB = mysql_select_db("library");


	$strSQL = "SELECT * FROM book WHERE book_isbn = '".$strProduct."' ";
	$objQuery = mysql_query($strSQL) or die ("Error Query [".$strSQL."]");
	$objResult = mysql_fetch_array($objQuery);
	if($objResult)
	{
		echo $objResult["book_name"]."|".$objResult["book_page"]."|".$objResult["book_type"]."|".$objResult["book_state"];
	}

	mysql_close($objConnect);
?>