Turn off and off RTS

I'm developing a simple program that uses the serial port to active a PCB that lights an LED.

I'm using the new Visual Studio Express VB 2005.

The PCB (printed circuit board) uses the toggling of RTS/GND on the serial port.

Until I understand how this works, I'm just trying to test this with a simple click of the mouse. Click inside the main form and the LED turns on and off.

Once I understand how it all works, I'll use the code to turn on and off RTS when a question is answered a particular way by the user.

For my testing, here is my code:

Private Sub Main_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseClick(My.Resources.sounderclick, AudioPlayMode.Background)

My.Computer.Ports.OpenSerialPort("COM1").RTSEnable = True

My.Computer.Ports.OpenSerialPort("COM1").RTSEnable = False

End Sub

Unfortunately, this isn't working. I thought it would be this simple. Perhaps it is and I'm missing something. COM1 is unused, so I should be ok...and I know it works as I've used a mouse and modem on that same port.

But, when I click in the form, during debug, I get the following:

UnauthorizedAccessException
Access to the port 'COM1' is denied.

If I enumerate the ports, I get COM1 and COM3. Using both COM1 and COM3 result in this same problem.

I'm new to VB programming so this error message is confusing me. When I read the help information it says that the operating system (in my case, XP Profesional with SP2) is denying access to the port.

I'm not sure how to fix this or where to look for answers. I looked several hours last night on MSDN and about everything I was finding was referring to files and not a serial port.

Please provide any assistance or guidance on where I should next proceed.

Thanks

Ted