recovering over-written file

I run a bar/restaurant and all our bookings are held on seperate excel files.
I've just made a huge mistake and accidently over-written the month of august file with novembers.

Is there anyway (using auto-recover possibly) that I can recover the original copy of the august file that I have over-written??

I hope there is, as otherwise i've just lost all records of August's bookings.

thanks, i'll give that a try.