[DllImport("user32.dll")]

    protected static extern IntPtr SetClipboardViewer(IntPtr hWndNewViewer);

    [DllImport("user32.dll")]

    protected static extern bool ChangeClipboardChain(IntPtr hWndRemove, IntPtr hWndNewNext);

    [DllImport("user32.dll")]

    protected static extern int SendMessage(IntPtr hwnd, int wMsg, IntPtr wParam, IntPtr lParam);

이거쓰면 될듯 ㅇㅅㅇ