Invoice screen and ability to change invoice before posting.

We need an Invoice screen. So that when goods are despatched from a sales order they immediately create an invoice, we then need to be able to access the invoice in the invoice screen to amend the price and then post the invoice to complete.The date on the invoice will then be taken from date of despatch rather than retrospectively amending the invoice date at the time of print as this is a laborious process. This invoice screen would be similar to Sage 50.