calculate difference between database-rows on output in an easy way?

[eluser]Richard Schumann[/eluser]
hi, i am richard and realy new to oop - i am addicted and wanna learn like the hell but for this problem what i even dont know how to call it in progammers language - i cant find a nice solution - may someone wanna give me some breakthrough to this ?

let me say i have a table ID(autoinc), VALUE(some numbers like 100,99,77 ...)

CONTROLLER

Code:

$this->db->from('table');
$data['query'] = $this->db->get();

VIEW

Code:

<?php foreach ( $query->result() as $row ): ?>
<?=$row->value?>
<?php endforeach; ?>

how would you best calculate and output the difference from one row to another to have a result like this :

99 +1
98 +28
70 -5
75 -35
40 -

- how to know / trigger next row result in foreach-loop to calc that direct in view ?
- or : how to prepare the array to add another field with the difference in controller?

thanks for your help