Highlight cells automatically that will forecast before a desired date.

Hi,
I have been serving as an aviation technician. Probably many of you know that some parts of airplane has a limited calendar life (e.g. 36 weeks, 72 weeks, 5 years, 10 years etc.). Maintaining these parts' life of different airplanes at the same time is difficult. So I have prepared a worksheet with formulas which contains all the data regarding the parts' life. Now, I want that the cell containing forecast date of parts life will be highlighted automatically before 15 days or 30 days prior to expiry date. For example, a fuel pump has a 3 years of life and the life of that fitted pump in the airplane will expire on 07-Sep-2021. My desire is that this cell of expiry date will be highlighted before 1 month (07-Aug-2021 and on....) in respect of my laptop/computer's system date.

How can I do that?

Welcome to the forum.

Which airline is this?

That's an airplane, not an airline.