Directory size

Hi guys!!!

Is there an easy way to know the size of a directory (with it´s files and subfolders, of course)?

One alternative is to look for the size of every file and subfolder on the directory with a recursive function, but maybe a miracle api call or something can do something faster.

Any ideas?

Looking for all the files is probably what the MS-Explorer
does when you open the properties window of a directory.
I think there is no other way.