You are looking at a script to do the backup.
The script can go through your files and copy the modified files to a new directory. As it copies it can add the days date to the end of the file name. It can also create a new directory with the date of copying as well.
But I would suspect just adding the days date to the end of the file name would be all you need.
If you think this is a good idea click on the Request Attention button and ask for this question to be added to the MSDOS
http://www.experts-exchange.com/Microsoft/Operating_Systems/MS_DOS/ and Windows Batch
http://www.experts-exchange.com/Programming/Languages/Scripting/Shell/Batch/ areas. Those guys can whip up a script to do what you want.