Thank you guys for the responses.

My problem is that as the machine is constantly running and windows is generally left open under the Default User's ID this will always return the Default User.

Yes I could check whether it's between 01:55am and 02:05am, and that is not a bad solution, but would frustrate any user trying to open the file at 02:00am as it would open briefly (hidden) and then close again.

I'm really just looking for an elegant one file solution.