must have a queries to select which BCC should be sent, base n the clients product
like :
$cartquery=msyql_query("select from cart_table where id='$sid' ");
while ($tempresult=mysql_fetch_object($cartquery)) {
$id=$tempresult->id;
$query=mysql_query("select from cart_table INNER join vendors on cart_table.id=vendors.id where cart_table=$id ") or die (mysql_error());
$result=mysql_fetch_object($query);
$email=$result->emailtable;
}
// now process email BCC here after checkout