I have a unique situation where I regularly need to create negative invoices (basically stating we owe the customer money).  Customers get charged monthly for activities 'A', 'B', and 'C', and get rebated for activity 'D'.  Under normal circumstances activity 'D' just reduces the total invoice amount and this all works beautifully.  However, it is not uncommon for 'D' to exceed the total billings on the invoice.  NetSuite does not allow invoices to be negative, which is very unfortunate for me because the invoice form is the simplest and cleanest way to present the monthly activity to the customer and