Additional discount on sales invoice?

help me guys on how to solve this. theres a customer that we give a 2 discount. ill create a 2 discount filed. question is it posible if i make this into custom script? and any idea about how to code this.

ill try to code in custom script. but the grand total still the same.


Grand Total is calculated at the server side, hence it will get over-written on the same. Rather you could use %Discount field in the Item table to apply double discount. We always suggest to try managing scenario with the so many standard features available in ERPNext. This also includes convincing the user to change the way they used to operate, for greater good.