How to avoid bill only line to create Invoice, and wait for other line

Hi Guru,

We have 3 lines in 1 sales order number such as:

1. standard line,

2. ship only

3. bill only

Client requirement is this 3 line must be in one invoice number number, and currently

we have custom program to override transaction number with sales order number in AR interface. So invoice number

same with sales order number. In workflow there is no header invoice interface for bill only.

Kindly advise how to achieve this requirement

Thank you