The NEGBINOMDIST function returns the negative binomial distribution. @f is the number of failures, @t is the threshold number of successes, and @p is the probability of a success.
If @f or @t is a non-integer it is truncated. If (@f + @t -1) <= 0 NEGBINOMDIST returns #NUM! error. If @p < 0 or @p > 1 NEGBINOMDIST returns #NUM! error.