How to control two devices with GPIB-UBS-HS+ in VB 2019 ?

Hai, I am working with Visual Basics 2019 to control two devices using GPIB-USB-HS+. I could control one device by following syntax.

Imports NationalInstruments.VisaNS

Dim GPIB_ResourceString1 As String

GPIB_ResourceString1 = "GPIB0::8::INSTR"

mbSession = CType(ResourceManager.GetLocalManager().Open(GPIB_ResourceString),

MessageBasedSession)

mbSession.Write("OUTX 0 ;")

response = mbSession.Query("OUTX ?").

Then how to control two devices with GPIBs? I could connect the two devices using two GPIBs, but not able to send command and read the response from a specific device. Can anyone help me in this? Thank you in advance.