Calculates the value of investments based on:

- a present value pv
- an interest rate compounded once per period - rate - enter as a decimal number, not percents
- total number of periods - nper
- a fixed payment amount - pmt
- when the fixed payment amount is paid - when - enter 0 when at the end of each period, enter 1 if at the beginning of each period

Negative numbers represents cash flow

**out**.