Test your Returns Formula(s)

motivated by a question from Mo
So I get this question about whether some formula for calculating returns is correct, or at least close, so ...
>So you make up a spreadsheet, right
Of course
>And, as usual, the spreadsheet had errors, right?
Uh ... yes.
Anyway, it may be useful to others. It looks like this:
You stick in your own formulas, in columns N, O and P.
Then, every time you press F9 you get a set of random returns
and the stock prices are plotted).
The real, live 1 and 3 and 5year returns are given
(a la XIRR ) in columns J, K and L.
>That's it?
Yup!
>And I click on the picture to get the spreadsheet?
Yup!
