Hi,
You need to create a derived table in the data foundation like this:
SELECT
A.Customer,
Max(A.Last_Transaction_Date) as Last_Transaction_Date,
Sum(Amount) as Amount
FROM My_Table B,
(SELECT Customer, Last_Transaction_Date
FROM My_Table
WHERE
Last_Transaction_Date BETWEEN @Prompt('Start Date','D') AND @Prompt('End Date','D')
GROUP BY
Customer,
Last_Transaction_Date) A
Where B.Customer = A.Customer And B.Last_Transaction_Date = A.Last_Transaction_Date
GROUP BY A.Customer
Then in the Business, Layer you create objects Customer,, Last Transaction Date and Amount based on the derived table.
And you will have only one row for a customer corresponding to the Max Last_Transaction_Date including on the dates range selected in the 2 @Prompt.
Didier