elseif statement not working

page1 form
 
<label>
                <input name="boxes" type="radio" value="New Intake" checked="checked" />
 				 Intake</label>
                <label>
                <input type="radio" name="boxes" value="Box Return" />
			  Return</label>
                <label>
                <input type="radio" name="boxes" value="Box Retrival" />
			  Retrive</label>
                <br />
                <label>
                <input type="radio" name="boxes" value="Box Destruction" />
  				Destruction</label>
                <label>
                <input type="radio" name="boxes" value="Box Supply" />
			  Supply</label></fieldset></p>
                
             <p><fieldset><legend><strong>Select Service Level</strong></legend> 
             
               <label>
               <input name="service" type="radio" value="standard" checked="checked" />
  				Standard</label>
<input type="textfield" name="box_add[]" size="25" multiple="multiple" id="box_add" />
----------------------------------------------------------------------
page2 statement
 
<?php 
 
if(isset($_POST['box_add']) && sizeof($_POST['box_add']) > 0)
{
    // To make sure the user did include the 'box'
    // We will need this variable later on!
    $shall_we_proceed = true;
 
    // Here, we will loop each box's value and query it to check whether exist or not.
    // Ofcourse, it might be slower than yours previous posting, whereby using only 1 statement.
    // Is up to you to use which algorithm you wish to validate it. ^^
    foreach($_POST['box_add'] as $val)
    {
        $sql = "SELECT custref FROM boxes WHERE custref='$val'";
        $qry = mysql_query($sql) or die(mysql_error());
        $nRecords = mysql_num_rows($qry);
        if(mysql_num_rows($qry))
        {
            echo '<span style="font-weight:bold;color: #ff0000;">' . 'That record already exists in the database: ' . '</span>' . '<span style="font-weight:bold;color: #000;">' . '('  . $val . ')' . '</span>' . '<br />' . '<span style="font-weight:bold;color: #ff0000;">' . 'Please select another' . '</span>' . '<p />';
            $shall_we_proceed = false;
            break;    // Quit the loop
        }
    }
 
    if($shall_we_proceed)
    {
        // Okay! We can proceed!
       echo 'You have Added ref: ' . '<span style="font-weight:bold;color: #000;">' . $val . '</span>' . '<p />';
		$_SESSION['box_add'] = $_POST['box_add'];
    } 
}
else
 
if(isset($_POST['box_add']) && ($_POST['boxes']) == 'Box Retrival' && sizeof($_POST['box_add']) < 0)
{
    // To make sure the user did include the 'box'
    // We will need this variable later on!
    $shall_we_proceed = true;
 
    // Here, we will loop each box's value and query it to check whether exist or not.
    // Ofcourse, it might be slower than yours previous posting, whereby using only 1 statement.
    // Is up to you to use which algorithm you wish to validate it. ^^
    foreach($_POST['box_add'] as $val)
    {
        $sql = "SELECT custref FROM boxes WHERE custref='$val'";
        $qry = mysql_query($sql) or die(mysql_error());
        $nRecords = mysql_num_rows($qry);
        if(mysql_num_rows($qry))
        {
            echo '<span style="font-weight:bold;color: #ff0000;">' . 'That record already exists in the database: ' . '</span>' . '<span style="font-weight:bold;color: #000;">' . '('  . $val . ')' . '</span>' . '<br />' . '<span style="font-weight:bold;color: #ff0000;">' . 'Please select another' . '</span>' . '<p />';
            $shall_we_proceed = false;
            break;    // Quit the loop
        }
    }
 
    if($shall_we_proceed)
    {
        // Okay! We can proceed!
       echo 'You have Requested ref: ' . '<span style="font-weight:bold;color: #000;">' . $val . '</span>' . '<p />';
		$_SESSION['box_add'] = $_POST['boxes'];
    } 
}
else
{
    // Error!
    echo "hey! please add box!";
}
 
 
?>