mouse hook - param problem

class globalMouse
    {
        public delegate int HookProc(int nCode, IntPtr wParam, IntPtr lParam);
        public delegate void MouseEventHandle(MouseHookStruct Info);

        [StructLayout(LayoutKind.Sequential)]
        public class POINT
        {
            public int x;
            public int y;
        }

        [StructLayout(LayoutKind.Sequential)]
        public class MouseHookStruct
        {
            public POINT pt;
            public IntPtr hwnd;
            public int wHitTestCode;
            public int dwExtraInfo;
        }

        const int WH_MOUSE = 14;

        int hhook = 0;

        public event MouseEventHandle MouseEvent;

        public globalMouse()
        {
            hook();
        }

        ~globalMouse()
        {
            unhook();
        }

        public void hook()
        {
            IntPtr hInstance = LoadLibrary("User32");
            hhook = SetWindowsHookEx(WH_MOUSE, hookProc, hInstance, 0);
        }

        public void unhook()
        {
            UnhookWindowsHookEx(hhook);
        }

        /*
         *
         *
         *
         * problem - lParam.hwnd = 0.
         * MyMouseHookStruct.hwnd = 0.
         *
         */
        public int hookProc(int code, IntPtr wParam, IntPtr lParam)
        {
            if (code >= 0)
            {
                if ((int)wParam == 0x204)
                {
                    MouseHookStruct MyMouseHookStruct = (MouseHookStruct)Marshal.PtrToStructure(lParam, typeof(MouseHookStruct));
                    MouseEvent(MyMouseHookStruct);
                }
            }
            return CallNextHookEx(hhook, code, wParam, lParam);
        }

        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        public static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);

        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        public static extern bool UnhookWindowsHookEx(int idHook);

        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        public static extern int CallNextHookEx(int idHook, int nCode, IntPtr wParam, IntPtr lParam);

        [DllImport("kernel32.dll")]
        static extern IntPtr LoadLibrary(string lpFileName);
    }