See if this works:
Private Sub ModbusTCPCom1_ConnectionEstablished(sender As Object, e As EventArgs) Handles ModbusTCPCom1.ConnectionEstablished
Label1.Visible = True
End Sub
Private Sub ModbusTCPCom1_ComError(sender As Object, e As Drivers.Common.PlcComEventArgs) Handles ModbusTCPCom1.ComError
Label1.Visible = False
End Sub