Combobox PHP

<form action="" method="post" >
<select name="cb_tabelas" >
         <option value="0">--Selecionar Categoria--</option>
<option value="1">Marcas</option>
<option value="2">Produtos</option>
<option value="3">Projectos</option>
<option value="4">Promoções</option>
<option value="5">Enventos</option>
<option value="6">Nossas Marcas</option>
</select>

<input name="editar" type="submit" value="Editar" />


<?php
include("mysql.php");
if(isset($_POST['cb_tabelas']))
{
$var1 = $_POST['cb_tabelas'];
switch ($var1){
case 0:

echo "Selecione uma Categoria que queira Editar";
break;
case 1:



$sql = "select * from marcas";
$query = mysql_query($sql);?>
<table width="99%" border="1" cellspacing="0" cellpadding="0">
<tr>
<th colspan="4" scope="col"><p style="background: url(images/img007.png) no-repeat left top;">Clientes</p></th>
</tr>
<tr>
<td width="9%"><input name="Delete" type="submit" id="Delete" value="Delete"></td>
<td width="9%"></td>
<td width="76%"> </td>
</tr>
</table>

<?php echo "<table width=\"99%\" border=\"1\" cellspacing=\"0\" cellpadding=\"0\">";
echo "<tr>";
echo "<th scope=\"col\" style=\"font-size:9px;\">#</th>";
echo "<th scope=\"col\" style=\"font-size:9px;\">id</th>";
echo "<th scope=\"col\" style=\"font-size:9px;\">Nome</th>";
echo "<th scope=\"col\" style=\"font-size:9px;\">Logo</th>";
       
echo "</tr>";

while($row = mysql_fetch_array($query)){


?>

<td align="center" ><input type="checkbox" name="arquivo[]" value="<?php echo $row['id_marca']; ?>"/></td>
               
<?php echo $row['id_marca']; ?>
<?php

echo"<td style=\"font-size:11px;\" style=\"text-align:center\">" ; echo $row['id_marca']."</td>";
echo"<td style=\"font-size:11px;\" style=\"text-align:center\">"; echo $row['nome']."</td>";
echo"<td style=\"font-size:11px;\" style=\"text-align:center\">"; echo $row['logo']."</td>";
       
echo"</tr>";
}


echo "</table>";
?>

<?php
if(isset($_POST['Delete']))
{

foreach($_POST['arquivo'] as $checkbox)
{
echo "OKKKKKKKK";
#mysql_query("DELETE FROM marcas WHERE id_marca='$checkbox'");
#echo "<META HTTP-EQUIV=Refresh CONTENT=\"0; URL=index.php?site=editar\">";


}}

if(isset($_POST['InserirCliente']))
{

echo "<META HTTP-EQUIV=Refresh CONTENT=\"0; URL=index.php?site=registar\">";
}
echo "</form>";
break;
case 2:
echo "Produtos";
break;
case 3:

break;
case 4:
break;
case 5:
break;
}
}?>