Clean objects from sub-folder

Hi,

I'm using the Arm DS IDE Gold Edition.

1. My project has some sub-folders like 'src, 'RTE' and so on that contains source files.
   Building the project is OK, however during 'Clean Project', the objects under these sub-folders are not cleaned.
   How shall i do so?
2. I would like to have a single 'obj' sub-folder within my project that all source objects goes there and cleaned from there during 'Clean Project'.
   How shall i do so?

Thanks,
Ronen