static class Program
    {
        /// <summary>
        /// Главная точка входа для приложения.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.AddMessageFilter(new TestMessageFilter());
            Application.Run(new Form1());
            
        }

        [DllImport("user32.dll")]
        static extern bool PostMessage(IntPtr hWnd, int Msg, IntPtr wParam, IntPtr lParam);

        const int WM_INPUT = 0x00FF;

        public class TestMessageFilter : IMessageFilter
        {
            public bool PreFilterMessage(ref Message m)
            {
                
                // Blocks all the messages relating to the left mouse button.
                
                if (m.Msg == WM_INPUT)
                {
                    Debug.WriteLine("Вот WM_INPUT");
                }
                return false;
            }
        }
    }