Vim does not recognize previous command when issued within a function

I can execute the following command and then enter "@:" to repeat the command.

This works fine.

:windo silent/foo/|wincmd w

@:

However, when I execute the same command within a function, "@:" displays an

error message saying there is no  previous command.

How can I get the command within the function to be registered as a command for "@:"?

function! Find_In_Multiple_Windows(pattern)

  if !empty(a:pattern)

    execute ":windo silent /" . a:pattern . "/|wincmd w"

  endif

endfunction

nnoremap <silent>fw :call Find_In_Multiple_Windows(input("Search for: "))<CR>

fw

Search for: foo

@:

E30: No previous command line

Note: Also posted on stackoverflow, but no responses so far.