I am a VB beginner. This routine returns error '8005, Port already open' at line PortOpen = True. If I use CommPort = 1, it gives me 'invalid Port number' at PortOpen = True. What is the problem?

Private Sub Form_Load()
CommCtrl.CommPort = 2
CommCtrl.Settings = "9600,n,8,1"
CommCtrl.InputLen = 0
CommCtrl.PortOpen = True
CommCtrl.Output = "ATZ" + Chr(13)
Do
DummyVar = DoEvents()
Loop Until CommCtrl.InBufferCount >= 2
InString$ = CommCtrl.Input
CommCtrl.PortOpen = False
End Sub