Paste this into paypal.php
$process_button_string = tep_draw_hidden_field('cmd', '_cart') .
tep_draw_hidden_field('upload', '1') .
tep_draw_hidden_field('business', MODULE_PAYMENT_PAYPAL_ID) .
tep_draw_hidden_field('currency_code', $my_currency) .
tep_draw_hidden_field('return', tep_href_link(FILENAME_CHECKOUT_PROCESS, '', 'SSL')) .
tep_draw_hidden_field('cancel_return', tep_href_link(FILENAME_CHECKOUT_PAYMENT, '', 'SSL')) .
tep_draw_hidden_field('shipping_1',
number_format($order->info['shipping_cost'] *
$currencies->get_value($my_currency),
$currencies->get_decimal_places($my_currency))) .
tep_draw_hidden_field('tax_cart', number_format($order->info['tax']
* $currencies->get_value($my_currency),
$currencies->get_decimal_places($my_currency)));
for ($i=0; $i<sizeof($order->products); $i++) {
$j = $i+1;
$process_button_string .= tep_draw_hidden_field('item_name_' . $j, $order->products[$i]['name']) .
tep_draw_hidden_field('item_number_' . $j, $order->products[$i]['model']) .
tep_draw_hidden_field('quantity_' . $j, $order->products[$i]['qty']) .
tep_draw_hidden_field('amount_' . $j, $order->products[$i]['final_price']);
}