Don't know of a free Add-in, but if Jon Peltier's manual instructions do
not meet your needs, you might look at the commercial Add-in "StatTools"
from Palisade
http://www.palisade.com/html/stattools.asp
which does box plots. I believe you can download a free time-limited trial.

Jerry

Jan Heijs wrote:

is there an add-inn available that creates a box and whisker plot.
This a grpahic representaion of statistic information showing the raange of
values per categorie.