Flag particular dates

I have set up a db at work, I work in a flying school. All students and
other pilots are included in this db, along with particulars such as Medical
Certificate expiry date. I need to have the db 'flag' those people whos
medical certificates will expire in say, 4 weeks time. Any help in setting
this up would be appreciated, or perhaps if there are any publications I
could buy, I would appreciate the information. Location: Adelaide, South
Australia.


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