You can use File Options to run a script when the file opens.
The script can perform a find for all employee records with a "reviewed date" 90 or more days older than the current date.
If any records are found, it can pop up the list of the employee records where review is needed.
The "reviewed date" field can auto-enter the hire date to get an initial value and then you can update it with the current date each time you do your employee review so that it is omitted from the next list this script pulls up.
Enter Find Mode //clear the pause check box
Set Field [EmployeesTable::ReviewDate ; "≤" & Get ( CurrentDate ) - 90 ]
Set Error Capture [on]
Perform Find 
If [Get (FoundCount ) = 0 ]
Go To Layout [Main Menu]