How do I measure wifi strength in vb.net?

 Public Function GetSignalStrength() As String
        On Error GoTo oops

        Dim query As ManagementObjectSearcher
        Dim Qc As ManagementObjectCollection
        Dim Oq As ObjectQuery
        Dim Ms As ManagementScope
        Dim Co As ConnectionOptions
        Dim Mo As ManagementObject
        Dim outp As String

        Co = New ConnectionOptions
        Ms = New ManagementScope("root\wmi")
        Oq = New ObjectQuery("SELECT * FROM MSNdis_80211_ReceivedSignalStrength Where active=true")
        query = New ManagementObjectSearcher(Ms, Oq)
        Qc = query.Get
        outp = ""

        For Each Mo In query.Get
            outp = outp & Mo("Ndis80211ReceivedSignalStrength") & " "
            ISIPActive = Mo("Active")
        Next

        Return Trim(outp)
        Exit Function
oops:
        Return Err.Description
    End Function