Values aren't being returned in Sub-Procedure

I have a two subroutines where one calls the other and passes 2 parameters, however, on return, the parameters are empty and I'm not sure what I'm doing wrong.

Here are the two Sub Routines:

    Private Sub usrResistanceCreep_ResistanceButton() Handles usrResistanceCreep.ResistanceButton
        'Debug.Print("usrResistanceCreep_ResistanceButton")

        Try
            Dim strRin As String = String.Empty
            Dim strRout As String = String.Empty

            EH.ErrorMessage = String.Empty

            CheckTestRinRout(strRin, strRout)

            If strRin.Length > 0 Then
                usrResistanceCreep.txtRIn.Text = Format(CDec(strRin), "#####0.####")
            End If

            If strRout.Length > 0 Then
                usrResistanceCreep.txtROut.Text = Format(CDec(strRout), "#####0.####")
            End If

        Catch ex As Exception
            EH.ErrorMessage = "frmCalibration_3/usrResistanceCreep_ResistanceButton() - " & ex.Message & "...Contact Engineering!" & "~E"
        End Try

        EH.ProcessMessages(Me, sbr, EH.ErrorMessage)
    End Sub
    '
    '
    '
    Public Sub CheckTestRinRout(ByVal strRIn As String, ByVal strROut As String)
        'Debug.Print("CheckTestRinRout")

        Try
            EH.ErrorMessage = String.Empty

            strMessage = "Acquiring Resistance In / Resistance Out values!"
            mlStatusMessage.Text = strMessage

            strRIn = String.Empty
            strRout = String.Empty

            Application.DoEvents()

            InitializeErrorClass(EH)
            ReadRin(RealReadMode, 0, EH)
            If EH.ErrorMessage = String.Empty Then
                strRIn = CStr(GetDecimalPlaces(CStr(EH.sSingle), gLoadDecimalPlaces))
            Else
                GoTo ProcessMessage
            End If

            If blnGetRout Then
                blnGetRout = False

                ReadRout(RealReadMode, 0, EH)

                If EH.ErrorMessage = String.Empty Then
                    strRout = CStr(GetDecimalPlaces(CStr(EH.sSingle), gLoadDecimalPlaces))
                End If
            End If

            If strRIn.Length > 0 And strRout.Length > 0 Then
                blnResiTestComplete = True

                If AreTestsComplete2() Then
                    btnSaveTestLoad.Focus()
                End If
            End If

            mlStatusMessage.Text = String.Empty

ProcessMessage:

        Catch ex As Exception
            EH.ErrorMessage = "frmCalibration_3/CheckTestRinRout() - " & ex.Message & "...Contact Engineering!" & "~E"
        End Try
    End Sub

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