You don't need a script: You just need to edit your crontab file, and to do that, you simply go:
The format is simple. Below is mine for running a mailscan using bitdefender every day:
35 12 * * * /usr/bin/mailscan
I have a one-line "script," if you want to glorify it with that name, that simply tells bitdefender only to check the mail files. That's what the /usr/bin/mailscan part refers to.
The numbers and asterisks mean: run it at 35 MINUTES past the hour of 12 NOON every day of every week of every month. (The asterisk is the typical wild-card thing, meaning "every.")
It's as simple as that: minute, hour, day, week, month. Then what you want done. Voilą!
Hope this helps.
Note that you MUST run crontab -e to edit the crontab. It's the only way it will "take."
It will very nicely tell you, too, if you make a mistake, which is a big plus. That way you won't have a bad crontab file without knowing it.