How to write a code for dynamic NPV()

Question

Hi, i'm new to vb.net and trying to use the present value function for my own use accounting application: PV = FV / (1 + x) ^ t. The FV will take place between 3 to 10 years investment and each year will be given a different amount of cash by the user. This PV later will be used to calculate the Net Present Value by substracting the initial cost amount given with the PV . I'm not familiar with array yet, so this is what i have wrote: Static valarray(5) As Double Dim rate, NPer, pmt, dblNetPresentValue As Double Dim dblPvResult, dblNPV As Double valarray(0) = Convert.ToDouble(nudOutlay.Value) valarray(1) = Convert.ToDouble(txtYearOne.Text) valarray(2) = Convert.ToDouble(txtYearTwo.Text) valarray(3) = Convert.ToDouble(txtYearThree.Text) valarray(4) = Convert.ToDouble(txtYearFour.Text) valarray(5) = Convert.ToDouble(txtYearFive.Text) rate = Convert.ToDouble(txtDiscountRate.Text) 'NPer(4) = valarray(4) pmt = nudOutlay.Value dblPresentValue = NPV(rate, valarray()) dblPvResult = dblNetPresentValue FV(rate, NPer, pmt) dblNPV = dblNetPresentValue - pmt lblDisplayNPV.Text = Convert.ToString(dblNPV) and i'm getting confused with all the PV(), NPV(), and FV() functions. Thank you for the help guys.