Checkbox in ALV OM can't be edit

I am using the ALV OM, and i user following codes to offer a check box in the output ALV ,which users can select the data from the list :

data: begin of itab

chek (1)

fields

...

end of itab

try.

lr_column ?= lr_columns->get_column( 'CHECKBOX' ). "a field where the * value can be either 'X' or ' ' (space).

lr_column->set_cell_type( if_salv_c_cell_type=>checkbox_hotpot ).

lr_column->set_long_text( 'CHECKBOX' ).

catch cx_salv_not_found. "#EC NO_HANDLER

endtry.

But it's so strange that <b>,this checkbox can't be edit or mark in list screen....How can I solve this problem??</b>

Appricate you help .Thanks in advance.