easy???Delphi Report!!!!

Well I have been trying and trying but I don' understand what's the problem

well I want to do a report like this

--------------
Client 1
 Import    50
 Import    20
 Import    10
 Import    10
   Subtotal 90
--------------
Client 2
 Import    40
 Import    20
 Import    10
 Import    10
   Subtotal 80
--------------
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That's all that I want to do,,, I did it with "Groups bands" and footer an detail and I tested the example that delphi 4 and delphi 5 contain....
The group is ok but the SubTotal is a total acumulate and it's not and subtotal by group....
i mean...
my report shows something like this
--------------
Client 1
 Import    50
 Import    20
 Import    10
 Import    10
   Subtotal 90
--------------
Client 2
 Import    40
 Import    20
 Import    10
 Import    10
   Subtotal 170
--------------
as U seen it's not that I want to show...It's wrong...
I used an expression to show the "Subtotal"....
Can U explain me how can I do it???