Setup Multiple Timers

I haven't started writing this macro yet, as I'm hoping for some guidance on how to start.

I have an Excel report listing various reports that need to be sent on a timely basis (weekly, monthly, annually, a specific date, etc.). I'd like to have timers set to mail out reminders to the responsible parties a few days in advance. I know how to do all of the email stuff, just not how to do the timers. Plus, the spreadsheet containing the report isn't opened every day, so I don't know how to automatically open the spreadsheet to trigger the timer to remind the person.

Can anyone help me get started?