Я бы использовал List (of) для этого:
Dim Ports As New List(Of IO.Ports.SerialPort)
Dim newport1 As New IO.Ports.SerialPort
newport1.PortName = "COM1"
Dim newport2 As New IO.Ports.SerialPort
newport2.PortName = "COM2"
Ports.Add(newport1)
Ports.Add(newport2)
'later in code, handle all ports with index in the Ports-list
Ports(0).Open() 'open port1
Ports(1).Open() 'open port2
или это немного по-другому:
Dim Ports As New List(Of IO.Ports.SerialPort)
Ports.Add(New IO.Ports.SerialPort)
Ports.Add(New IO.Ports.SerialPort)
'later in code, handle all ports with index in the Ports-list
Ports(0).PortName = "COM1"
Ports(0).Open()
Ports(1).PortName = "COM2"
Ports(1).Open()