Automatically update a field based on time elapsed since a particular date
I have two tables in my FM13 database - "Individuals" and "Donations". I have a portal set up in "Individuals" that displays all the donations (ordered by ascending "Disbursement Date") that a person has made (connected with a primary key). I also have a "Donor Status" field in my Individuals table: a drop-down menu with options like Current, New, Lapsed, Non-donor). I want to set it up so that if an individual's Donor Status = "Current Donor" but they haven't made a donation in more than 18 months, Filemaker will automatically update their Donor Status to "Lapsed Donor". Is this possible? I started trying to set up a nested If calculation to achieve this but I've only been working with Filemaker for a couple of weeks so I don't understand calculations and scripts very well yet and I'm not sure that's the most elegant way to do this. Any help is appreciated.