Since this is a coupon, it won't work when doing a PM. Doing a price match, either by the "normal" way or via a manually-changed price, it invalidates the use of a coupon on the transaction. You can either do a PM or use a coupon, not both.
The only way for it to happen would be for someone to manually change the price of the item to the cost of the item after the coupon's deduction from the PM'd price. It would be taking $40 off a $60 item, putting it below their cost and it would require a key-turn/manager approval to have it work. Once that happens, you'd likely get shot down.