I am not good at VB and need help with this code

Private Sub findMortgagePayment()
        Dim prompt As String
        Dim validPV As Boolean = False
        Dim validAPR As Boolean = False
        Dim validTerm As Boolean = False
        Dim principal As Double
        Dim apr As Double
        Dim term As Integer

        Try
            '***********************************************************************
            'implement input validation and set local variables  here
            '***********************************************************************
            If validatePrincipalAmount() Then
                principal = Double.Parse(txtMortgageAmount.Text)
                validPV = True
            Else
                txtMortgageAmount.Clear()
            End If
            If validateInterestRate() Then
                apr = Double.Parse(txtInterestRate.Text)
                validAPR = True
            Else
                txtInterestRate.Clear()
            End If
            If validateTerm() Then
                term = Integer.Parse(txtMortgageTerm.Text)
                validTerm = True
            Else
                txtMortgageTerm.Clear()
            End If
           
            If validPV AndAlso validAPR AndAlso validTerm Then
                '***********************************************************************
                ' declare and create a new mortgage data object  
                ' invoke this class's displayPayment method
                ' invoke this class's displayAmoritizationTable method
                '***********************************************************************
                Dim mortgageData As MortgageData
                mortgageData = New MortgageData()



            Else
                lblAmount.Text = ""
                ToolTip1.SetToolTip(lblAmount, "")
                ToolTip1.SetToolTip(rtfAmortTable, "")
                If Not validPV Then
                    prompt = "Please re-enter the loan amount information and try again"
                    InputUtilities.ShowErrorMessage(prompt, "Invalid Loan value")
                    txtMortgageAmount.Focus()
                ElseIf Not validAPR Then
                    prompt = "Please re-enter the interest rate information and try again"
                    InputUtilities.ShowErrorMessage(prompt, "Invalid Interest rate value")
                    txtInterestRate.Focus()
                Else
                    prompt = "Please re-enter the term length information and try again"
                    InputUtilities.ShowErrorMessage(prompt, "Invalid Term value")
                    txtMortgageTerm.Focus()
                End If
            End If
        Catch ex As Exception
            prompt = "Please re-enter the loan information and try again"
            InputUtilities.ShowErrorMessage(ex, prompt)
            ClearFields()
        End Try
    End Sub

    Private Sub displayPayment(ByRef mortgage As MortgageData)
        lblAmount.Text = FormatCurrency(mortgage.Payment, 2)
        ToolTip1.SetToolTip(lblAmount, "Monthly payment is: " & lblAmount.Text)
    End Sub

    Private Sub displayAmortizationTable(ByRef mortgage As MortgageData)

        Dim tableOutput As String

        '***********************************************************************
        'create AmortizationTable here
        'retreive the Amoritization table
        '***********************************************************************

        rtfAmortTable.Text = tableOutput
        ToolTip1.SetToolTip(rtfAmortTable, "Amortization Table for " & mortgage.FullDataString)
    End Sub

#End Region

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