Hi Paul,

I'm part of the UI Team over at humyo.com. The problem that you are
describing is caused by Excel locking the file while it's being used,
this is done to prevent any other application making changes to the
file while you have it open. As soon as you close the file humyo will
instantly start syncing the file online.

Our Development Team do plan to improve this in the future by
implementing "shadow copying" functionality which would get around the
file lock, how ever I'm not currently aware of any time scales for
this feature.

You would be best getting in touch with out support team or
subscribing to the SmartDrive change log to be notified of any future
improvements.

The changelog for the Windows version of SmartDrive can be found here
- http://blog.humyo.com/category/changelog/win/