Problem with set analysis - max expression

[sankar_ganesh]

Product	Sales_Date	Sales
a	03/20/2014	10
a	03/20/2014	5
a	03/19/2014	20
a	03/18/2014	30
b	02/28/2014	40
b	02/28/2014	20
b	02/20/2014	50
b	02/10/2014	60

Hi, The above table is the example source data for my report...i need to find the sum of sales  occured on the latest sales date of each product to obtain the result shown below..

Result table to be shown:

Product	SalesAt_LatestDate
a	15
b	60

sum({<Sales_Date={'$(=maxstring(Sales_Date))'}>}Sales)

i used the above expression but i get only the the first row given in the result table as the maxstring(Sales_Date) is evaluated for the whole data not for each product. Does anyone have any idea to resolve this issue i.e. to evaluate the max(sales_date)  for each product ?

[Gysbert_Wassenaar]

sum(if(Sales_Date=aggr(nodistinct max(Sales_Date),Product),Sales))

[Nicole-Smith · Accepted solution]

sum({<Sales_Date={'=Sales_Date=aggr(maxstring(Sales_Date),Product)'}>}Sales)

Example file also attached.

[SunilChauhan]

sum({<Sales_Date={$(=Max(Sales_Date))}>}Sales)

make sure date format is not text