Delayed Invoicing

[Tom_Page@xxxxxxxxxx]

We have a product that we do not want to invoice until the customer
receives the product and accepts.
We are on 6.101 MM.  Our normal process is to batch our invoices at night
with BIL500 and all shipments for that day are invoiced.
I have tried to get the billing selection flag to work as a filter, so I
could code normal orders with an 'N', this is defaulted from the
customer master.  At first I had some issues with the RMA / credit  orders
posting as the older RMA's were not set with the new billing
selection flag, but I got that right.  Atrer a week I discovered that our
freight charges were not being applied to our invoices.  We use the
special charges ECS file to attach our freight at the line level.  I can
not  get these records to invoice without leaving the billing selection
field blank at BIL500.
Any suggestions or another way to approach this problem, with only some
orders to have delayed invoicing?

Thanks -Tom