[VBA] Macro to apply discount to Order Form

!UPDATE!

I have a sample order form with products, quantity, prices & discounts in the attached file.

I need help in creating a macro such that, when a discount value is entered in C18 and the button is clicked:

1. the values in column F will be deleted
2. the discount percentage in C18 will be applied to the value in C16
3. this discounted amount will be spread over the totals of Product Offering C to A in column I

4. meaning that if the value in C16 is 10,000 and 50% is entered in C18, and the total of Product Offering C - A are 2000, 3000 and 5,000 respectively (the sum is then the value in C16 =10,000).
5. the discount value will be 5,000
6. 2000 of the discounted value (5,000) will be applied to first to Product Offering C. (meaning the sum of Product Offering C will 100% discount)
7. the remaining 3000 of the discount value will then be applied to Product Offering B. (again, meaning a 100% discount it)
8. it should always follow this order: Product Offering C --> Product Offering B ---Product Offering A


I hope the explanation of the problem is quite clear.

I would appreciate any help with this. Thank you.