Change/Add Extra Theme Directory

Hello,

I don’t have any substantial knowledge in PHP yet, but I’ve tried digging up the codes, trying to find where to change the themes directory for wpmu. Its got to be somewhere in themes.php ??

I tried changing the $stylesheets … defined in themes.php but it seems like there’s some more codes that needs to be revised in order to change the themes directory?

Could somebody please help. I want a drop down box that we can choose a theme directory so that themes have options such as Space, Flowers, or Nature.

Thanks.