Visual Basic.NET - Estoy haciendo un programa que me calcule el periodo de gracia de un prestamo pero no lo e podido l

LoanAmount = Convert.ToDecimal(txtMonto.Text)

LoanIRate = Convert.ToDecimal(txtTasaInteres.Text)

LoanDuration = CInt(txtPlazo.Text)

Montoinicial = LoanAmount

'llama la funsion que calcula el interes mensual

Intrest = Percen.Percentage(LoanIRate)

Payment = (LoanAmount / LoanDuration)

Dim principal, interes, i, p As Double

dtgviewtable.Rows.Clear()

For Period = 1 To LoanDuration

	'Pago mensual

	IntPmt = (Payment + Intrest)

	'calcula el interes

	interes = LoanAmount * Intrest

	principal = Payment

	'calcula el saldo

	LoanAmount = LoanAmount - principal

	If Val(txtPeriodoGracia.Text) = 3 Then

		i = interes * Period

		p = Val(txtTasaInteres.Text) * Val(txtMonto.Text)

	End If

	Dim FechaInicial As Date = Date.Today

	'aqui adiciono un mes a la fecha.

	FechaInicial = DateAdd("M", Period, Date.Today)

	'aqui, me posiciono en el primer dia de la fecha a la que le voy adicionando el mes

	FechaInicial = FechaInicial.AddMonths(0)

	Dim b As Integer = dtgviewtable.Rows.Add

	dtgviewtable.Rows.Item(b).Cells(0).Value = Period

	dtgviewtable.Rows.Item(b).Cells(1).Value = (FechaInicial.ToString("D", CultureInfo.CreateSpecificCulture("es-MX")))

	dtgviewtable.Rows.Item(b).Cells(2).Value = (Format(Montoinicial, Fmt))

	dtgviewtable.Rows.Item(b).Cells(3).Value = (Format(IntPmt, Fmt))

	dtgviewtable.Rows.Item(b).Cells(4).Value = (Format(interes, Fmt))

	dtgviewtable.Rows.Item(b).Cells(5).Value = (Format(principal, Fmt))

	dtgviewtable.Rows.Item(b).Cells(6).Value = (Format(LoanAmount, Fmt))

Next