I think you dont need to go full round to check not invoiced deliveries.
VBFA is table for sales document flow and there is one filed called VBTYP which indicates types of document.
please find following important type
A Inquiry
B Quotation
C Order
D Item proposal
E Scheduling agreement
F Scheduling agreement with external service agent
G Contract
H Returns
I Order w/o charge
J Delivery
K Credit memo request
L Debit memo request
M Invoice
N Invoice cancellation
for invoice document type is M ,and for invoice preceding document is delivery , so this table makes use of concept preceding and subsequent documents.
this table to my knowledge will give you deliveries which are not invoiced.
talk to your functional consultant and get some test data , like get some
completed invoice - delivery documents
uncompleted invoice - delivery documents
pass to this table and observe , based on that you can built the logic.