You can track this metric using your DMS. We track it in Dealerbuilt. You need to use two separate fields for pricing in the inventory screen. We also used to do it in Reynolds. In Dealerbuilt, when we stock a car in, we put the original asking price in the Inventory MSRP field as well as in the Advertised Sale Price field. Any subsequent price changes should be made in the Advertised Sale Price field. This way, when we sell the car, we can cross reference the selling price with the Last Advertised Price as well as the Original Asking Price. Dealerbuilt generates a nightly spreadsheet that gets emailed out to us and then we use an excel macro to process the formulas and formatting. I know throughout the month what my "GAP" is off last advertised price as well as original asking price. I'm more focused on GAP off original asking price these days because that metric speaks more to the ability to price the car right to maximize front gross and promote turn. I hope this helps.