Use this method to merge a set of data records one after the other into the mail merge template. Use the first and last parameters to delimit the range of table records that you want to use. You must already have passed the table using the method set_data_source.

CALL METHOD mail_merge->merge_range
       EXPORTING first      = first
                 last       = last
                 no_flush   = no_flush
       IMPORTING retcode    = retcode
                 error      = error.