I need to know how to create this info below as we are running a promotional deal and need to apply this method in my New Sales Orders: 

QTY: 3 master Cartons (2 Tropical Punch and 1 Blue Raspberry) and show the Special Discount after the Sub-Total, showing the deduction of -$216.00, and the Grand total having it at $432.00 instead of $648.00?

Can someone help?

Thank you,

Nader