Calling a user function via a map cancels visual mode

I have the following function and mappings:

function! JumpToNextNonMatching(direction)
let flags = ''
if a:direction == -1
let flags = flags . 'b'
endif
let ntimes = max([v:count, 1])
let i = 1
while i <= ntimes
let i = i + 1
let curr_line = getline('.')
let spattern = '^[^' . curr_line[0] . '][^' . curr_line[1] . ']'
call search(spattern, flags)
endwhile
endfunction
noremap ,n :<C-U>call JumpToNextNonMatching(1)<CR><C-L>
noremap ,N :<C-U>call JumpToNextNonMatching(-1)<CR><C-L>

The idea is simply to jump to a previous or next line not matching the beggining of current line.

But if I am in visual mode and use one of the mappings then visual mode is cancelled.
Any suggestions on howto properly define the function of the mapping so when I use it I stay in visual mode (with the selection resulting of applying the map, of course).

Thanks,
Jorge

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