{assign var="firstCustomField" value="true"}
{foreach from=$cf_invoice item="cfield"}
<div class="field{if $cfield.is_required} required{/if}{if $firstCustomField} first{/if}">
<label>{$cfield.field_caption|htmlspecialchars}</label>
<div>{cfield field=$cfield}</div>
</div>
{assign var="firstCustomField" value="false"}
{/foreach}