public static void SendMouseInput(int positionX, int positionY, int maxX, int maxY, bool leftDown)
        {
            if (positionX > int.MaxValue)
                throw new ArgumentOutOfRangeException("positionX");
            if (positionY > int.MaxValue)
                throw new ArgumentOutOfRangeException("positionY");

            Input[] i = new Input[2];

            // move the mouse to the position specified
            i[0] = new Input();
            i[0].Type = InputMouse;
            i[0].MouseInput.X = (positionX * 65535) / maxX;
            i[0].MouseInput.Y = (positionY * 65535) / maxY;
            i[0].MouseInput.Flags = MouseEventAbsolute | MouseEventMove;

            // determine if we need to send a mouse down or mouse up event
            if (!lastLeftDown && leftDown)
            {
                i[1] = new Input();
                i[1].Type = InputMouse;
                i[1].MouseInput.Flags = MouseEventLeftDown;
            }
            else if (lastLeftDown && !leftDown)
            {
                i[1] = new Input();
                i[1].Type = InputMouse;
                i[1].MouseInput.Flags = MouseEventLeftUp;
            }

            lastLeftDown = leftDown;

            // send it off
            uint result = SendInput(2, i, Marshal.SizeOf(i[0]));
            if (result == 0)
                throw new Win32Exception(Marshal.GetLastWin32Error());
        }
 private static extern uint SendInput(uint numInputs, Input[] inputs, int size);