Without thinking through the whole scenario, I reckon I'd start by tracking the hours in their own separate table so that each record contains employeeID, datePerformed, and whatever other links and data are relevant to the situation—so you can track the relevance of particular hours to particular credentials, for example. Then I'd set up a date calc in the employee table that was current date minus five years, and then use that to flag records in the hours table that were older than that date, or within a month of that date, or whatever. Then I'd show employees hours in a portal sorted by date worth oldest showing first. Something along those lines.
So I've actually done something similar, but am stuck on the last part - putting it on a report.
There is a field that is is calculated by today's date, less five years. It is a text field, and the value is either "Valid" or blank.
I could easily filter a portal, but we are looking to have only the oldest "Valid" date appear on a report, along with other information that needs to be tracked about each employee.
I tried the following "if" calculation:
It returns the oldest date if all training was completed within the last five years. However, once any training time is outside of five years, it sets the value of that field to blank.