First, take at look at this.
After you've made the change to allow the class to be exposed properly, you
set a reference to the code database by selecting Tools|References and
locating your MDE containing the classes.
Note that if you change or recompile the code database containing your
classes, you must recompile ALL databases that reference it. So, creating a
DLL is really the better option. However, if the objects in your code
database are stable/unlikely to change, you'd probably be safe to reference
it in multiple projects. But remember again, if you reference the code
database in multiple databases, and make changes or recompile the code
database, you'll have to recompile all of them.
Personally, I only use code databases as a means to organize a large project
where all the component databases get recompiled at the same time anyway.
