Using formula field to delay notification

The way our developer would probably handle this would be to have a php script running under cron on a Linux server. It would run, say, every 15 minutes and look for any records in your table that have a date-time value in your formula field on or before the current time that hadn't been processed yet. And you'd need another date-time field that the script would update for [Notification Sent]. Then, set up a notification rule that would fire whenever this Notification Sent field had been updated.

I wish we could do cron-like event handling in QB natively, but alas....