Could work, but I would use dropbox instead since windows sharing is so messy imo 
This is a bat file that first:
- Copies the bank file from the dropbox folder and replaces the local bank file if it's newer
- Starts sc2
- pauses the bat(leave the window open and press enter when you are done playing sc2)
- copies the local bankfile to the dropbox folder
Code:
xcopy /d /y DROPBOXPATH LOCALPATH
"PATH TO Starcraft II.exe"
pause
xcopy /d /y LOCALPATH DROPBOXPATH
When you close sc2 just press enter in the window and it will copy your updated bankfile to the dropbox folder.
Make sure the bankfile with the highest score is the one that is most recently updated, or this script will fail.
Backup your bankfile to a safe place, incase something goes wrong