the on timer event would work if you can guarantee that the application will be open 24/7.
There is nothing fancy about the macro approach.
Take your email code (everything without the evaluation part since you won't need it when utilizing the scheduler).
Paste it into a new public function in a new module e.g.:
Public Function ScheculedEmail()
'your email code
Then close and save the module as something different then the function within it.
Create a new macro...in the action argument pick RunCode...in the Function Name property write the name of your function you just created e.g. ScheculedEmail(). When automating this with the scheduler you should add another action to the macro or the function itself which shuts down the application after it is done with its process to make sure it doesn't stay open.
Now you can create a new batch file and call your created macro with the macro command line switch e.g.:
CD\Program Files\Microsoft Office\Office
Msaccess.exe C:\Northwind.mdb /x YourMacroName
Then schedule the batch file. You can read a little more detail about this process here