<#assign subtotal = 0>
<#assign lastGroup = "">

<#list record.lines?sort_by('project')>
  <#if lastGroup && lastGroup != line.project>
    <#-- print subtotal -->
	
	<#assign subtotal = 0>
	<#assign lastGroup = line.project>
  </#if>
  
  <#-- regular line logic here -->
  
  <#assign subtotal = subtotal + line.amount>
</#list>