Remove all products on a new invoice

Remove all products on a new invoice

We are a services company and when we send out invoices they are usually for 1/3 or 1/4 the balance of a sale, so the default behavior of converting a sales order to an invoice adds line items that are irrelevant to the way we work. I would like to create a custom button that can either:
  • Remove all product items from the invoice currently being created
  • Or: Read a "Terms" field on the sales order and create multiple invoices, each representing the pricing breakdowns (1/3 or 1/4 the Grand Total)

I'm hoping this is possible and would appreciate any help in getting this set up.

Thanks!