Controlling other control,when receiveng data from serial port.

Question

Hi all,,
I am writing a program that can communicate through serial port. I have manage the port connection, I try to send a string from my phone, and show the string on the textbox. I have successfully done that.

What I want to achieve is,when i receive the data from my phone, I want to control others windows control, such as, enabling the timer.

my code look like this.

        private void Form1_Load(object sender, EventArgs e)
        {
            _serialport.DataReceived += new SerialDataReceivedEventHandler(_serialport_DataReceived);
            _serialport.PortName = "COM4";
            _serialport.BaudRate = 9600;
            _serialport.DataBits = 8;
            _serialport.Parity = Parity.None;
            _serialport.StopBits = StopBits.One;
            _serialport.Open();
        }
        private delegate void SetTextDeleg(string text);
        private void _serialport_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
            
           
            string data = _serialport.ReadExisting();
            // Invokes the delegate on the UI thread, and sends the data that was received to the invoked method.
            // ---- The "si_DataReceived" method will be executed on the UI thread which allows populating of the textbox.
            this.BeginInvoke(new SetTextDeleg(si_DataReceived), new object[] { data });
            timer1.Enabled = true;
            
        }
        private void si_DataReceived(string data) 
        {
            textBox1.Text = data.Trim();
            timer1.Enabled=true;
        }
        private void timer()
        {
            if (textBox1.Text == "makan")
                timer1.Enabled = true;
        }
        private void timer1_Tick(object sender, EventArgs e)
        {
            if (sec > 58)
            {
                min++;
                sec = 0;
            }
            else
            {
                sec++;
            }
            if (min == 2 && sec > 29)
            {
                lblTime.ForeColor = Color.Red;
            }
            if (min == 3)
            {
                min = 3;
                sec = 0;
                lblTime.Text = string.Format("{0:00} : {1:00}", min, sec);
                timer1.Enabled = false;
            }
            lblTime.Text = string.Format("{0:00} : {1:00}", min, sec);
        }

I also have try to enabled the timer in si_DataReceived, but also failed. How is the correct way to do it? Thanks.