Applying discount to Order Form with VBA

Hi

I have an order form with products, quantities and prices in the attached file.

I would like help in figuring out how to apply one discount value to the whole order, such that if a value is entered in the grey field, the following should happen:
This value will overwrite all discounts in the discount column
Discount in the grey cell should first apply to all Product Offering C --> Product Offering B -->Product Offering A

I haven't created any macro for this.

I appreciate any help with this.

Thank you
Attached Files