The trick with triggering this is to decide what FM program event should be used to trigger the test of the date.
The most consistent may well be to have it fire as a subscript of the file's startup script -- a script triggered when the first program window of the file is opened.
You would probably also want to test for a user group which could run this subscript, as you don't want it firing everytime anyone logs in.
You also will want a field in the record to record that the email was sent, probably a timestamp field, and you will then exclude records from being emailed which have already been emailed.
Another, probably cleaner, solution would be to script this process without any file trigger, and then setup a Server schedule to run this script and send email notifications at a set frequency, such as 1am each day.
You're better off having a server script run a script that checks for the field value in the field and if it matched your criteria, send the email through SMTP.
Thanks guys for the info! After thinking about it I think the server script would be the way to go. That way I don't have to wait for someone to open the database for notifications to be sent. Good call.