RDLC group report and tota

I am developing a report using Visual Studio 2010 ..... for example

Dataset Having Data as 

1234                  ABCD                   100

1234                  DEFG                    115

4321                  PQRS                   200

i want to show data in my rdlc as 

1234                  ABCD                      215

                          DEFG

4321                   PQRS                     200

Please Help i am able to group column 1 but how can i get  the sum based on that group and want to show that sum as the above example