-- prepare test data

declare @t table (PRODUCT_CATEGORY_ID tinyint, PRODUCT_CATEGORY_NAME varchar(9), PRODUCT_CATEGORY_AMOUNT money, COMMISSION_MONTH datetime)

set dateformat dmy

insert	@t
select	1, 'Product A', 54985, '1/10/2004' union all
select	1, 'Product A', 349050, '1/09/2004' union all
select	1, 'Product A', 167645, '1/08/2004' union all
select	2, 'Product B', 65206.94, '1/08/2006' union all
select	2, 'Product B', 258028.73, '1/07/2006' union all
select	2, 'Product B', 246538.22, '1/06/2006' union all
select	7, 'LINE', 283506.69, '1/08/2006' union all
select	7, 'LINE', 314186.78, '1/07/2006' union all
select	7, 'LINE', 260485.38, '1/06/2006' union all
select	7, 'LINE', 319169.2, '1/04/2006' union all
select	7, 'LINE', 332763.64, '1/03/2006' union all
select	7, 'LINE', 329983.35, '1/08/2004' union all
select	7, 'LINE', 319307.68, '1/07/2004' union all
select	9, 'CONTRACT', 25950, '1/08/2006' union all
select	9, 'CONTRACT', 20350, '1/07/2006' union all
select	9, 'CONTRACT', 4550, '1/06/2006' union all
select	9, 'CONTRACT', 248000, '1/04/2006'

-- do the work
select		t.PRODUCT_CATEGORY_ID,
		t.PRODUCT_CATEGORY_NAME,
		t.PRODUCT_CATEGORY_AMOUNT,
		t.COMMISSION_MONTH,
		case
			when w.product_category_id is null then ''
			else cast(t.PRODUCT_CATEGORY_ID as varchar) + ' ' + t.PRODUCT_CATEGORY_NAME + ' ' + cast((select sum(r.PRODUCT_CATEGORY_AMOUNT) from @t r where r.product_category_id = t.product_category_id and r.commission_month >= w.peso) as varchar) end
from		@t t
left join	(
			select		product_category_id,
					dateadd(month, -2, max(COMMISSION_MONTH)) peso
			from		@t
			group by	product_category_id
		) w on w.product_category_id = t.product_category_id and w.peso = t.COMMISSION_MONTH