Jitka wrote...
need to calculate fact(365) but getting #Num!. Any advice?

Do you really NEED to calculate 365!, or are you working with numbers
of the form n!/[(n-k)!k!] ? If the latter, and if you refuse to use
any of the standard algebraic reductions common in either probability
or combinatorics, you could probably get by using GAMMALN since ln(n!)
= GAMMALN(n+1), so n!/[(n-k)!k!] = ROUND(EXP(GAMMALN(n+1)/GAMMALN(n-k
+1)/GAMMALN(k+1)),0). The ROUND call is needed because Excel's GAMMALN
is only accurate to 10 decimal places and is really poor around 1 and
2 where it should return 0 exactly.