<#if item?has_next>
  <#assign nextItem = record.item[item_index+1]>
  <#if item.item == nextItem.item && item.class == nextItem.class && item.memo == nextItem.memo>
    <!-- all fields match, now do a #list?take_while to sum all the amounts -->
    <#assign summedAmount = item.amount>
	<#list record.item[item_index..]?take_while(nextItem => 
	  item.item == nextItem.item && item.class == nextItem.class && item.memo == nextItem.memo) as nextItem >
      <#assign summedAmount += nextItem.amount>
    </#list>

    <!-- do your regular item row output here, but now using ${summedAmount} -->
	
  </#if>
</#if>