Assistance with MsgBox in Program

[vbendurer]

OK, it's the newbie to programming. I have written a program to calcuate and display the montly payment and total interest paid on a loan. I have to put in a note that says if interest rate is below .06 that "Interest Rate Must Be 6% or higher." I don't have a problem with the message but after the message is displayed and I hit ok, it still calculates the amount. How do I get it to either, return to program to input new interest rate then complete program: Code is as follows:

Public Class frmLoan

    Private Sub btnAnalyze_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnAnalyze.Click

        Dim p, r, n, payment, ti As Double
        ' Set MSGbox if percentage is off
        If r < 0.06 Then
            MsgBox("Interest rate must be 6 percent or higher", MsgBoxStyle.Exclamation, "WARNING")
        Else

        End If

        'set value parameters for calculation
        p = CDbl(txtloan.Text)
        r = CDbl(txtRate.Text) / 12
        n = CDbl(txtLength.Text) ' duration of loan
        payment = (p * r) / (1 - (1 + r) ^ (-n))
        ti = (n * payment) - p


        'display results from formula calculations
        With lstResults.Items
            .Clear()
            .Add("Total monthly pay is " & (FormatCurrency(payment) & "."))
            .Add("")
            .Add("Total interest is paid is " & (FormatCurrency(ti) & "."))

        End With

    End Sub
End Class