GAMMAINV function

Returns the inverse of the gamma cumulative distribution


 * GAMMAINV seeks that value x such that GAMMADIST(x, alpha, beta, TRUE) = probability. If the search has not converged after 100 iterations, the function returns the #N/A error value.
 * If any argument is text, GAMMAINV returns the #VALUE! error value.
 * If probability 1, GAMMAINV returns the #NUM! error value.
 * If alpha ≤ 0 or if beta ≤ 0, GAMMAINV returns the #NUM! error value.