ปัญหา INSERT ข้อมูลซ้ำกันหลายๆครั้ง ควรแก้ไขหรือกำหนดขอบเขตอย่างไรครับผม

<?
session_start();
?>

<script type="text/javascript" src="js/jquery-1.2.6.min.js"></script>
<script type="text/javascript" src="js/jquery.livequery.js"></script>
<script src="js/jquery.elastic.js" type="text/javascript" charset="utf-8"></script>
<script src="js/jquery.watermarkinput.js" type="text/javascript"></script>
<script type="text/javascript">
	

	$(document).ready(function(){	
	
		//SubmitComment
		$('#SubmitComment').click(function(){
			
			
			var user = $("#user").val();
			var mcode = $("#mcode").val();
			var id = $("#id").val();
			var count = $("#count").val();
			var getpID =  $(this).parent().attr('id').replace('commentBox-','');	
			var comment_text = $("#commentMark-"+getpID).val();
			
			if(comment_text != "Write a comment...")
			{
				$.post("add_comment.php?comment_text="+comment_text+"&post_id="+getpID+"&id="+id+"&user="+user+"&mcode="+mcode+"&count="+count, {
	
				}, function(response){
					
					$('#CommentPosted'+getpID).append($(response).fadeIn('slow'));
					$("#commentMark-"+getpID).val("Write a comment...");					
				});
			}
			
		});	

		

	});	

	// ]]>

</script>

<div class="commentBox" align="right" id="commentBox-<?php  echo $Mcode;?>">
					<input type="hidden" id="count" name="count" value="1" />
					<input type="hidden" id="user" name="user" value="<? echo $_SESSION['MM_Name']; ?>" />
        			<input type="hidden" id="id" name="id" value="<? echo $_GET['id']; ?>" />
					<input type="hidden" id="mcode" name="mcode" value="<?php  echo $Mcode;?>" />
					<textarea class="commentMark" id="commentMark-<?php  echo $Mcode;?>" name="commentMark" cols="60"></textarea>
				
				<br clear="all" />
				<a id="SubmitComment" class="small button comment"> Comment</a>
</div>
            
<div id="CommentPosted<?php  echo $Mcode;?>"></div>

 

<?
include('./config.php');
		
		$searchSQL = mysql_query("SELECT * FROM tbl_account WHERE Name = '".$_REQUEST['user']."' LIMIT 1");
		while($info = mysql_fetch_array($searchSQL))
		{
			$NameF = $info['Name'];
			$NcodeF = $info['Ncode'];
		}
		$searchSQL2 = mysql_query("SELECT * FROM tbl_account WHERE Ncode = '".$_REQUEST['id']."' LIMIT 1");
		while($info2 = mysql_fetch_array($searchSQL2))
		{
			$NameU = $info2['Name'];
			$NcodeU = $info2['Ncode'];
		}
		$Msg = $_REQUEST['comment_text'];
		$MMcode = $_REQUEST['mcode'];
		$Date = date("Y-m-d H:i:s");
		
		$strSQL = mysql_query("INSERT INTO tbl_comment (Name, Ncode, Friend, Fcode, Message, Mcode, Date)
		VALUES ('".$NameU."','".$NcodeU."','".$NameF."','".$NcodeF."','".$Msg."','".$MMcode."','".$Date."')");
		
		
		}
		
	


	?>