How can I hide the IME Candidate window

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VisualC++

hello,
In my program(VC++), I want to hide the IME Candidate window when I press FN key, and show my own Candidate window which list the other context; and where I press Fn key once more, then show the IME Candidate window and hide my own Candidate window .

But I cannot find the method of hiding IME Candidate window. who can give me some suggest? thank you so much.