How to set Report to show Sales Orders Pending Billing as at a particular date?

Hi There

I have a requirement where:

A report is needed showing all the sales orders which:

• have a status of either fulfilled or partially fulfilled.
• At the date the report is run, the sales orders need to be unbilled

The account has the accounting preference to allow invoices prior to fulfilment, checked.

My understanding is that you can't run a report to show data "as at" a specific date? (other than AR or AP aging reports).

is that correct?

Is it possible to modify the 'Open Sales Order' Report to show this information?

Thanks