I tried a few searches and couldn't find anything, although I imagine someone has brought it up so I apologise in advance.

Is there anyway or anything to create subfolders in your contacts list?

Basically I don't want to turn out phoning any work contacts accidentally when I'm drunk. I've got fat fingers when I'm drunk and there's too many people who's name starts with the same letter.

I'd be hoping to create a subfolder for them - either by app or code - to keep them out of harms way. If possible, a code entered to access the folder would also be good!