Black-Scholes equation?
N(d1) = the normal cdf of - infinity < x < d1 in excel you can find this by =NORMSDIST(enter your d1) Or you can look up d1 in a normal distribution table. The link below will help you approximate N(d1) if you round d1. The last page is what's important. The other note to make is if d1 or d2 is negative N(d1) = 1 - N(-d1)