How to find distinct sum of amount??

kish

Hi All,
i have birt report data like below

Supplier1
order1 ...... 1000
order1 ...... 1000
order1 ...... 1000
order2 ...... 3500
order2 ...... 3500
sum of total 10,000
the sum of total field is agregated on supplier1 field.Total.sum() function in sum of total picking all the values and displaying 10,000.But i want distinct values to be picked for different orders like 1000+3500 = 4,500 should come as sum of total value.
how to achive this.Any help is appreciated.