Dustin beat me to a solution. I was going to propose a Select-Case like this:
Select Case DrumNo
Case 1
TempController1.CommComponent = EthernetIPforCLXCom1
Case 2
TempController1.CommComponent = EthernetIPforCLXCom2
End Select
If you wanted to treat the drivers as an array, you would need to create an array, then assign each driver instance like this
Private Drivers(10) As AdvancedHMIDrivers.IComComponent
Private Sub MainForm_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Drivers(0) = EthernetIPforCLXCom1
Drivers(1) = EthernetIPforCLXCom2
.
.
.
End Sub
From there you could use similar code like you had:
TempController1.CommComponent = Drivers(DrumNo)