ABAP : Add Line items based on same material in .CSV File

Dear All,

      I have a requirement to export ABAP report to .CSV Excel Format. I have successfully exported the data to .CSV format. My .CSV file has first two lines as header,the data records are populated after the header data.The file has many fields . I want the Quantity field needs to be added up for the same Material No. 

My .CSv file looks like as Below..

Eg1.  Header Data...

       Billing DOC No.    Quantity    Material    Field1   Field2  and So on.

       1234                      12           M1              F1      F2             

       1234                      10           M1             F1      F2

Eg2:   Header Data...

       Billing DOC No.    Quantity    Material    Field1   Field2  and So on.

        3456                      4            M2            F1        F2   

        3456                       5           M3            F1        F2

       But i need it as below

Eg1 : Header Data ...

      Billing Doc .No.          Quantity      Material         Field1     Filed2 So on.

      1234                            22            M1                F1           F2

Eg2 :

     Header Data ...

      Billing Doc .No.          Quantity      Material         Field1     Filed2 So on.

       3456                            4             M2                  F1          F2

       3456                             5            M3                 F1           F2

Same Billing Doc No. can have different Material Number ...

I want the same  Material Number quantity needs to be added up and the different Material Number Quantity to retain same as shown above.

Please Give Suggestions.

Regards,

Amba