How much of this do you already know how to do?
Can you set up a script to find records?
Can you set up such a script to find all records with a date in a particular range of dates?
Can you "schedule" your script to run on a regular interval?
And what happens to the data in this table once you have found such records?
You'll need to make some kind of change so that they aren't found again the next time that you run this script. Do you need to record today's date in the RetestDate field to keep the records from being pulled up again?
For starters, here's a thread on scripted finds that you may find useful. It includes examples where the current date is used in different ways to search for records: Scripted Find Examples