Hello Franck,
For the query solution, problem is : datas come from differents cubes, differents system i don't have one multiprovider to support a query bex.
Thank for your idea to, first, consolidate the list of member to start my comparison, it will help.
I did some tests and now, i'm able to detect if i don't have the selected country in my DS_2, but i keep this thread because i think it can be helpful for other people if we succed to create a function which can compare 2 crosstabs