Take a look at this thread Find A Share size in Win2k. There is a method there by jsprat that is blindingly fast if the shared directory is the root of the remote drive.
Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." -Richard Buckminster Fuller