I don't know if I need to be in Excel programming or another section, but
here it is...

I want to solve a modular arithmetic problem in Excel (so i have been told
by a math professor).

Specifically, I want to solve for t (time) in the present value formula.
However, i (interest) is not constant, otherwise I'd use the log function.

I want (i) to increase, let's say every 2nd, 3rd, or 4th, year, which makes
this problem a modular arithmetic problem.

I've set up a table to determine the value of (t) given my variable (i) but
I was looking for a more direct approach. Any ideas anyone?