I have a large quoting template, with multiple pages, which provides the cost
of a part when the sales rep enters a part number.

Because some of the quotes get very large, there are 120 rows in which the
sales rep could potentially enter a part number. With that many rows, people
tend to miss marking up the cost of the product and then end up quoting it to
the customer at our cost.

I need some sort of reminder for the salespeople to markup the cost of a
part if they have entered a quantity next to a part number.

The rows below the following column headers require manual entry:
Column A = Quantity
Column B = Part Number
Column N = Customer Markup

Does anyone have any recommendations on what sort of formula, or conditional
formatting I could use to help easily notify the rep if they haven't entered
a % in Column N when there is a Quantity in A?