Working copy as sum of several folder in repository, how to do?

[Marilena Nardelli]

Hi, I want to use SVN in this way:

1.  in repository is stored project and some part of it (for examples, a folder with files to manage a sensor, a folder to mange a device - a radio module-, a folder to manage  an external eeprom, etc.);
2. on local folder I want to make a new project that is sum of more modules in repository, as i tested, if I use "export command" everithing works fine, but if I try with "checkout command" for every folder I need, I'm getting an error (the message informe me that the working copy had a different URL). QUESTION: I can use different command or I can't do that with SVN?
3. I suppose that point 2 could be overtake, and I do changes in one or more files that correspond to different module, I could use a "commit command" or some other?
4. Moreover, if a module is used in different projects and I update it from my working copy, how can inform all projects that are using it of new update? I can use a command, a particular procedure or I can't do that?

I hope my english is sufficient to explain my aim... thanks for any help.

Marilena