How do I read the response from a serial device?

I have a hardware device that will eventually control my application. Before I do that, I want to be able to control the settings on the device via simple commands.

A typical setting can be made by typing:
B1\n (where B is the setting, 1 is the value and \n is a new line to actually send the command)

This all works fine, but what I want to do is query what the setting is first before I set it. I'm able to do this via HyperTerminal by typing
B\n
this returns "=3" on the same line.. This is strange, as I told it to use a newline. It must be removing the newline and ammending "=3" to the "B" i just typed.

If I use SerialPort.ReadExisting() on the DataReceived event it returns simply "B". I'm sure it has something to do with the strange behaviour (above) but I dont know how I can grab the full output.

public bool Initialise()
        {
            Port = new SerialPort("COM4", 9600, Parity.None, 8, StopBits.One);
            Port.DataReceived += new SerialDataReceivedEventHandler(Port_DataReceived);
            try
            {
                Port.Open();
                return true;
            }
            catch (IOException ex) { return false; }
        }
 
        private void Port_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
            string data = string.Empty;
            while (Port.BytesToRead > 0)
            {
                data += Port.ReadExisting().Trim();
            }
        }

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