First, create your Macro in Access and test it to make sure it's doing what you want.
Now, assuming you don't mind leaving your Workstation turned on overnight to do the work for you at 6AM, this will work.
Write a .BAT file to run Access using your database and the macro you specify.
The command line syntax you need in the .BAT file is:
"C:\Program Files\Microsoft Office\Office\MSAccess.exe" "C:\My Documents\MyDatabase.mdb" /x MyMacro
Your paths to Access and the database are probably different. You can name your macro anything you like, but it's generally a good idea to use some naming convention so others know it's a Macro. I prefix all Macros with mcr, like mcrKensCoolMacro. And do include the quote marks around pathnames with long file names.
Use Task Scheduler to run your .BAT file at the times you specify throughout the day. I have several that run throughout the day. Task Scheduler and Access do the work for me.
HTH,