What kind of invoicing?  AP?  Matching Invoices with PO Receipts? AR?  With shipments?  Services?

What are your challenges?

Generally, your Sage Partner / Reseller should be able to help you with this kind of thing.  (We have this kind of conversation with our customers, advising on changes, with possible customizations to Sage including potential Enhancements from 3rd party developers).

Candy, Kevin M is asking some things that need to be known before the conversation can get started. I'd add a question about Sales Orders and customer pick ups. There's a lot to be known.

That being said, I've had to be creative with a client using Sage 100 (formerly Sage 90) for sales order / shipping / invoicing over the last 7 years. There were a lot of problems to overcome in order to make the system simpler to use and less fussy, for lack of a better term. I'd be interested in talking it over with you to see if my deep and wide experience can help you. 

Jim W
Independent Consultant, Sage 100, Starship, Scanforce, MS SQL, MS ACCESS

You should start with your local reseller.  It is not cost effective to bring in someone from out of your area who does not have any prior knowledge of your operation. You will be paying them to learn what your reseller probably already knows.