How do I create a pop up warning box with cell information?

[Rikki727]

I'm trying to set up a worksheet for our company's skills matrix. When the
expiry date for a certain item is less than 50 days away I want a pop up
warning box displaying which item for which employee is about to expire and
how many days are left.

 

[Gary''s Student]

We can use conditional formatting. For example if the expiration date is in
B1, then in C1 enter:

="expiration in " & B1-TODAY() & " days"

Then format C1 like:

Format > Conditional Formatting... > Formula is>
=B1-TODAY()>50
and pick a font color to match the background color.

This warning will be invisible until you approach the expiration date.