function! Box_clear ()
    mapclear!
    map <space> :<C-U>call Flip_box()<CR>
    map a i[ ] <ESC>hhh
    set laststatus=2
    set statusline=%f\ %=\ \[ChkB[x]\ spc,a]\ (%v,%l)
endfunction
call Box_clear()

function! Flip_box ()
    s!\[ \]![xXx]!e
    s!\[x\]![ ]!e
    s!\[xXx\]![x]!e
endfunction