Client requires a pre-bill AR invoice which also shows the prepayment amount due but also pulls in p

Our client requires a pre-bill AR invoice which also shows the prepayment amount due but also pulls in projects time.  Trying to determine how that can be done.  There is no "prebill" project type in projects. 

Could be along this path: if invoice type = Deposit, lines section would bring in lines a,b,c but I don't know how that could bring in project details.