upload data from excel

i have to upload the data from excel file so i m having the below code:

PARAMETER :p_prfile(128) TYPE c LOWER CASE DEFAULT

'C:\Documents and Settings\nlv09435\Desktop\Junk data\so_cancel.xls'.

START-OF-SELECTION.

lv_input = p_prfile.

CALL METHOD cl_gui_frontend_services=>gui_upload

EXPORTING

filename = lv_input

• filetype = 'XLS'

• has_field_separator = 'X'

• has_field_separator = lv_tab

CHANGING

data_tab = i_vbak[].

LOOP AT i_vbak.

WRITE :/ i_vbak-vbeln , i_vbak-posnr.

ENDLOOP.

but its not working its printing the junk data