On Sun, 14 Dec 2008 10:22:16 -0500, Dana DeLouis
wrote:

If anyone is interested. This problem should converge to a solution
quickly even if we (or Excel) are not accurate in our derivative. I
believe there is a logic bug somewhere in Excel's IRR algorithm.
However, the nature of this particular problem does allow us to have a
more exact derivative. Here is one method where we can be more exact...

=MyIRR(A1:A10)

Thanks, Dana
--ron