Big Troubles on designing Query about special customers' counting

Question

Hello buddies:
I meet a problem on designing Query about special customers' counting. Let me describe the requirment first.  I want to create a query with BEX , and there is a key figure with very special logic.
That is: to list the counts of the customers which has more than one sales records in a time period from sales data. 
For example :
when the user excute the query , he or she must input a time period ( 2007.01~2007.03 e.g)
then the query output as follow:
District          Cust-sount
North-Zone       100
South-Zone      120
The Main trouble are :
1. Threr are no document number in the detail of sales data document records. so I could not count the sales times with document number.
2. The time period is not fixed value, it depends on the user's input, so I can not define the counting logic in the update rule or in the query with fixed time period.
Anybody who met similar requirement pls show me your hand and give your solutions, thanks very much.
Jason

Answer 1

Hi,
    Your solution sounds a good way to count the distinct customers. but in my case, one salse line item must not be recognize as one sales record, instead,  one customer's all sales line items occurs in one day must be  recognize as one sales record ( or we say that one sales behavior).
for example:
customer     product    quantity   date
cust001       prod001        10       2007.06.06
cust001       prod002        20       2007.06.06
the two line items above means one sales record for the customer "cust001".
so I could not simply use the CKF : (( Counter ) *FV2 ) > 1 .
Best Regards,
Jason