basic excel penalty calculator

[mcaps]

I am putting together an excel sheet to calculate interest on amounts due. I understand that IRS calculates/compounds interests daily and that the rate changes every quarter plus an additional percentage amount. I have a couple questions;

1- Where can I get historical quarterly rates?
2- What is the additional amount percentage amount for individuals?

I am using the following as a reference,
http://www.irs.gov/irm/part20/irm_20-002-006r.html

Again this is to guestimate amounts due.
Total="P * (1 + I/p)^(p*Y)"
P - PRINCIPAL(uppercase)
I - INTEREST, ANNUAL
p - compounding periods per year(lowercase)
Y - YEARS

thanks,
mcaps