I want to have data validation on a cell containing a formula. Is it
possible to have validation on the results of a formula and how do you do it?
Here is what I'm doing:

A1 (QTY) A2 (UNIT PRICE) A3 (EXTENDED PRICE)

A3 HAS THIS FORMULA =A1*A2

I want to have any value exceeding $5000 in A3 cause a data validation error
alert to appear with a message instructing what to do.