Sub TestIPMT()
    Dim APR, PVal, Period, IntPmt, TotInt, TotPmts As Double
    Dim PayType As DueDate
    Dim Response As MsgBoxResult

    ' Usually 0 for a loan.
    Dim Fval As Double = 0
    ' Define money format.
    Dim Fmt As String = "###,###,##0.00"
    PVal = CDbl(InputBox("How much do you want to borrow?"))
    APR = CDbl(InputBox("What is the annual percentage rate of your loan?"))
    If APR > 1 Then APR = APR / 100 ' Ensure proper form.
    TotPmts = CInt(InputBox("How many monthly payments?"))
    Response = MsgBox("Do you make payments at end of the month?", MsgBoxStyle.YesNo)
    If Response = MsgBoxResult.No Then
        PayType = DueDate.BegOfPeriod
    Else
        PayType = DueDate.EndOfPeriod
    End If
    For Period = 1 To TotPmts   ' Total all interest.
        IntPmt = IPmt(APR / 12, Period, TotPmts, -PVal, Fval, PayType)
        TotInt = TotInt + IntPmt
    Next Period

    ' Display results.
    MsgBox("You will pay a total of " & Format(TotInt, Fmt) & 
        " in interest for this loan.")
End Sub