sample size formula

Without knowing the specific type of distribution of your data, or the standard deviation if it's mathematical data, I'm not seeing an applicable excel function. Furthermore, are you replacing samples, etc? However, I googled it for you and found:

http://www.surveysystem.com/sscalc.htm#one

583

Additionally, I found Slovin's Formula:
http://www.ehow.com/way_5475547_slov...echniques.html

n = N / (1 + Ne^2)

n = Number of samples
N = Total population
e = Error tolerance

Also, here's a wonderful list of equations from some random PDF hit:
http://www.uky.edu/~jmlhot2/courses/...la%20Sheet.pdf

I assume you're good enough with excel to program in the equations yourself as needed. But that should highlight the equations to use.