ขอวิธีการ Query SQL ของ checkbox หน่อยได้ใหมครับ ผมคิดไม่ออกจริงๆ

<?
include('connect.php');
include('formB1.php');
//$id = $_GET["txtCode"];
//$LastUpdate = $_POST["txtDate"];
$Company = $_POST["txtName"];
$CurAdd1 = $_POST["txtAddress"];
$Tel = $_POST["txtPhone"];
$Fax = $_POST["txtFax"];
$Email = $_POST["txtEmail"];
$Website = $_POST["txtWeb"];
$ContactPerson1 = $_POST["txtConnect"];
$ContactPosition1 = $_POST["txtPosition"];
$Credit = $_POST["txtCredit"];
$Remark = $_POST["txtComment"];
$Active = $_POST["checkbox"];

		$sql = "SELECT MAX(CustID) FROM tbcustomer";
		$query = mysql_db_query($dbname, $sql) or die("Can't Query");
		$cus_id = mysql_fetch_array($query);
		$id = $cus_id[0] + 1 ;
		
		$sql=	"	INSERT INTO tbcustomer ( CustID, Company, Credit, CurAdd1, ContactPerson1, ContactPosition1, Tel, Fax, Email, Website, Remark, 
					LastUpdate, Active )
					VALUES ( '$id', '$Company', '$Credit', '$CurAdd1', '$ContactPerson1', '$ContactPosition1', '$Tel', '$Fax', '$Email','$Website',
					'$Remark', now(), 'I' )
				";
		$query = mysql_db_query($dbname, $sql) or die("Can't Query");
		if($query)
		{
			echo "	<script language='javascript'>
					alert('Success');
					window.location='menu_formB.php';
					</script>
				 ";
		}else
		{
			echo "	<script language='javascript'>
					alert('Fail');
					window.location='fromB1.php';
					</script>
				 ";
		}
mysql_close();
?>