Internationalization module + custom path (path with slash pages/ES for spanish, and nothing for english)

Hi, i'm migrating a site to Drupal. I need pages has following urls:

english:

1. http://domain/about.asp
2. ....
3. http://domain/index.asp

spanish:

1. http://domain/pages/ES/about.asp
2. ....
3. http://domain/pages/ES/index.asp

All work for now if i put only ES in prefix path in spanish. but if i put pages/ES doesn't work. Any solution for this? A hacking for this internationalization module? I need a quick solution for this..

Thanks in advance.
Javi