The GAMMAINV function returns the inverse of the cumulative gamma distribution. If GAMMAINV does not converge (accuracy within +/- 3x10^7) after 100 iterations, the function returns #N/A! error.
If @p < 0 or @p > 1 GAMMAINV returns #NUM! error. If @alpha <= 0 or @beta <= 0 GAMMAINV returns #NUM! error.