Referring data fields from sub report in main report

Friends,

I'm facing a situation here wherein i have to refer data fields from Sub report to main report. Below is the detailed scenario

Main Report :

Currency 1        Subreport_A. Calc_Amount ( summary field from A subreport)

Currency 1        Subreport_B. Calc_Amount ( summary field from A subreport)

                        Difference ( A-B )

Currency 2        Subreport_A. Calc_Amount ( summary field from A subreport)

Currency 2        Subreport_B. Calc_Amount ( summary field from A subreport)

                        Difference ( A-B )

Currency 3        Subreport_A. Calc_Amount ( summary field from A subreport)

Currency 3        Subreport_B. Calc_Amount ( summary field from A subreport)

                        Difference ( A-B )

Subreport A:

Currency 1          Calc Amount   

Currency 2          Calc Amount

Currency 3          Calc Amount

Subreport B:

Currency 1          Calc Amount   

Currency 2          Calc Amount

Currency 3          Calc Amount

Please let me know how can i make this work?

I tried using shared variables , but they ended up carrying only one single value ( Not the whole data field).

Thanks in Advance,

Bharath