Sales Invoices Design Modification

Need to have the Sales Invoice designed so we can enter a Work Order Number AND Customer PO Number.  These are two important fields that have been asked to be included for years.  

The shipping date and Salesman fields on the Sale Invoice are redundant  to most companies.  PLEASE MODIFY THE SALES INVOICE TO INCLUDE INFORMATION THAT IS ACTUALLY REQUIRED BY OUR CUSTOMERS.

Please make this form user friendly.  There is no sense in customizing the invoice form if we cannot have the required information entered on it......