I usually make a separate Access database that links to this other database (it really just is another version of the "Front End Database"), runs upon opening, executes code, and then automatically close.
You can do that with an AutoExec macro (any macro named "AutoExec" automatically runs upon opening it), or by putting the VBA code in the Load event of a Form, and set that Form to be the Startup Form that the database opens to).
Then you can use any Scheduling program to open the database at the time you want it to run.
So it will open it at your designated time, run the code, and automatically close itself.
I have used this method with great success many times.