you could add an if statement that first checks the date stamp on the file and compares it to the current date, if they match, it does not copy, if the do not match, it copies the file.
*****BAT file Below****
@Echo Off
REM Sets variable for date in the mm/dd/yyyy
REM format
SET usedate=%DATE:~4,2%/%DATE:~7,2%/%DATE:~10,4%
REM checks for existance of the file desired
REM And copies output of DIR command
REM to a file called testcond.txt (makes a
REM logfile, overwritten each run)
dir c:\dir1\dir.txt /TA > c:\dir1\testcond.txt
REM looks in the logfile and looks for
REM todays date at the beginning of the
REM first text string
findstr "%USEDATE%" c:\dir1\testcond.txt
REM IF the dates of the files do not match
REM the file copies newfile.txt into
REM c:\dir1 and renames it dir.txt
REM thus overwritting the existing file
if "%errorlevel%" equ "1" (move c:\dir2\newfile.txt c:\dir1\dir.txt)
*****end batch file*****
this is a rough outline you can run with
just change paths and such, hope it helps.