If the folder has no other folders in it, the status bar will show the folder contents size from the Folders side of Explorer, otherwise I think that's the only way. Oh, you could also open the folder and quickly select all, but again, only if there are no folders in the folder.
Don't know any other ways, but that doesn't mean they dont' exist...
<font color=blue>Outside of a dog, a book is man's best friend. Inside the dog its too dark to read.
-- Groucho Marx</font color=blue>