Project Billing- Deriving GL Data from Invoice Date

We have the situaiton where we want to be able to generate an invoice with an invoice data that is in the future. For examle, we generate the billing with a through date of 31-Jan-2010  but with an invoice date of 14-Feb-2010.  This results in a GL date of Jan-2010.  What we want to be able to do is have a GL date of Jan-2010. 

At the point we generate the invoice only the period for Jan-2010 would be open. We are billing for a Joint Ventrure therefore require a future invoice date.

Does anyone know of any way that we could achieve this?