Sorry my database and php programming are very bad. And i can't understand your example

// initilize total
$total = 0;

(loop begins)

// add each cost to the total
$total += $hm->Zb('rs:def:cost');

(loop ends)

// display total
echo $total;

It's not full code. I add it to file that you wright to me, but the result was = 0. I can understand what i must do.

Can you help me, please.

What I meant by the loop is this:

<?php while( $hm->zb('@rs:def:begin_table') ) { ?>
....................
....................
....................
....................
<?php } ?>

By the way, you need to know the basic of PHP programming to do this type of modifications. If you haven't learned it yet, then please ask a PHP prgrammer to do the job.