Sum of Amount group by Currency

Hi,

In my report I want to show sum of amount by currency code. But my amount is display field. Anybody have any idea.

Customer Account               Currency                   Amount
1101                                        USD                           100
1102                                        USD                           200
                                                 Total                           300

1103                                         INR                           200
1104                                         INR                           200
                                                   Total                         400