В бэкэнде вы должны предоставить какой-то блок.
config.xml
<config>
...
<adminhtml>
<layout>
<updates>
<YOUR_MODULE>
<file>YOURLAYOUT.xml</file>
</YOUR_MODULE>
</updates>
</layout>
</adminhtml>
</config>
design / adminhtml / default / default / layout/YOURLAYOUT.xml
<layout>
<adminhtml_sales_order_view>
<reference name="order_totals">
<block type="adminhtml/sales_order_totals_item" name="invoice_fee" template="YOUR/MODULE/total.phtml" />
</reference>
</adminhtml_sales_order_view>
</layout>
design / adminhtml / default / default / template / YOUR / MODULE / total.phtml
<tr>
<td class="label"><?php echo $this->__('Invoice Fee') ?></td>
<td class="emph"><?php echo $this->displayPriceAttribute('invoice_fee', true) ?></td>
</tr>