You can add the project into both solutions if you like or you can just add a reference to the assembly on the second project.  This would really depend on how much you would be changing the BO library classes.

Yes, I have a solution with two projects, I want both use the same BOs

If you are referring to having a BO library then using those BOs in more than one solution, then yes.  You would just add a reference to the projects to which you want to use those BOs.  Let me know if I am not understanding your question.

Sorry, I Write in the title TOW, I mean Two..

Excuse me

Is possible to do that, and how?

I can't see the Bo from one project in the other one.

Thanks SF