FTP_R3_TO_SERVER : Uploading binary file (.XLS)

Hi Experts,

Im using FTP_R3_TO_SERVER FM to upload an Excel file from the user desktop.

CALL METHOD cl_gui_frontend_services=>gui_upload
       EXPORTING
         filename                = g_file
       IMPORTING
         filelength               =  g_len
       CHANGING
          data_tab                =  g_data
       EXCEPTIONS
         file_open_error         = 1
         file_read_error         = 2
         no_batch                = 3
         gui_refuse_filetransfer = 4
         invalid_type            = 5
         no_authority            = 6
         unknown_error           = 7
         bad_data_format         = 8
         header_not_allowed      = 9
         separator_not_allowed   = 10
         header_too_long         = 11
         unknown_dp_error        = 12
         access_denied           = 13
         dp_out_of_memory        = 14
         disk_full               = 15
         dp_timeout              = 16
         not_supported_by_gui    = 17
         error_no_gui            = 18
         others                  = 19
             .
     IF sy-subrc <> 0.
       message 'Error occured while uploading file' type 'S'.
       leave LIST-PROCESSING.
     ENDIF.

call function 'FTP_R3_TO_SERVER'
     exporting
       handle         = w_hdl
       fname          = wrk_file          "file path of destination system
       character_mode = ' '
       BLOB_LENGTH = BLOB_LEN
     tables
       blob =g_data
     exceptions
       tcpip_error    = 1
       command_error  = 2
       data_error     = 3
       others         = 4.

How to find the BLOB_LEN ? Now the file is getting uploaded.. but only partial data is there.

Please help