just look on their website. It depends if you have a "network licence" or not:

http://www.xlstat.com/en/network-licence.html

It costs almost double as the single user licence.

@ Anne Tromelin: Thank you so much, but I have to pay more to Addin soft or not?

Hi all,

My answer may not be what you would expect but here is my advise.

Download R (free of charge) and use it!

http://cran.r-project.org/

Whatever XLSTAT does, R does. Plus you can get help on the forums, there are plenty of examples and fan websites that you can use.

And you'll never have to pay anything again to do your stats :)

Cheers,

SCM