鼠标挂钩回调不被调用？

Question

我试图像这样钩住鼠标：

#include <windows.h>
#include <stdio.h>

HHOOK mouseHook;

LRESULT WINAPI MouseHookProc(int nCode, WPARAM wParam, LPARAM lParam)
{
    MessageBox(0, "Not Called :-(", "M", 0);

    return CallNextHookEx(mouseHook, nCode, wParam, lParam);
}

int main()
{
    mouseHook = SetWindowsHookEx(WH_MOUSE,
                                 (HOOKPROC)MouseHookProc,
                                 GetModuleHandle(NULL),
                                 0);

    printf("Press enter to exit.\n");
    getchar();

    return 0;
}

但是消息框永远不会出现。 我认为一切正常，但似乎出了点问题。

提前致谢。