Total orders in three weeks for a customer that was new three weeks ago.

Question

I need help figuring out the MDX to use to calculate this measure: Total orders in three weeks for customers that were new three weeks ago.   I seem to be having a brain freeze or over thinking this as usual. 
My records have a customer, a date, a flag=1 if they are new that order.  So I have a customer dimension a date dimension and four measures: Unique_customer, date, New_customer(the Flag), Orders. 
So the fact table would look something like this:
Date        Cust_Key       New_Flag      Order     
1/5/10      801                                     1           
1/5/10      802                  1                  1
1/5/10      803                                     1
1/6/10       801                                    
1
1/6/10      804                   1                  1
1/6/10       803                                     
1
1/6/10       802                                      1
1/7/10       801                                       1
1/7/10        802                                     
1
1/7/10       804                                       
1
And for simplicity, using days instead of weeks -
Customer 802 has a new flag 3 days ago and on report date 1/7/10 and has three orders, one per day. So my new measure should show 3
Customer 804 wouldn't show up until report date 1/8/10 and Customer 802 would drop off.
So I need to know how many times, to the current report week, did a customer who was new in LAG(3) place orders. 
Diane Blackwood

Answer 1

Thing will be easy if you have New_customer_Flag in customer dimension. The New_customer_Flag
should be 1 for all those customers who were new three weeks back.
Assuming that the measure you have is Count_Of_Order, MDX would be
Select [Measures].[Count_of_order] on Columns,
[Customer_Dim].[Customer].Members on Rows
From 
(Select ([Date_Dim].[Week].&[201001].Lag(3): [Date_Dim].[Week].&[201001])
on Columns
From [OrderCube])
Where ([Customer_Dim].[New_customer_Flag].&[1]);
Saurabh Kamath