You are correct. This feature is not officially documented. Here is a recent thread that discusses this feature in further detail

http://amazingcharts.com/ub/ubbthreads.php?ubb=showflat&Number=4478&page=2#Post4478

Vinny Meyer wrote this feature, and he was working on some other ones as well. Perhaps they will make it into the next version of Amazing Charts.

Brian Cotner, M.D.
Family Practice