Hi there,
I would second Neville's approach in regards to your question, MBBOWLER2001. I believe going with the Vendor Posting Group as your basis for differentiating your "Vendor Classes" is the best way to go. It allows you to accomplish several things in one fell swoop:
1) Use an existing field in the Vendor table without resorting to creating your own custom field
2) Be able to filter on this field in several ways, be it in the Vendor List or from the many vendor-related reports that exist in NAV (Vendor Purchase List, Vendor/Item Statistics, Vendor - Detail Trial Balance, Aged Accounts Payable and Vendor Purchases by Item come to mind...)
3) Be able to differentiate between each of the Vendor Class based on the A/P accounts you designate to each Vendor Posting Group. This also allows you to "eyeball" your Chart of Accounts without the need to resort to dimensions, if your dimensions are pre-assigned and extremely precious. If you can spare a dimension for it, then all of the Vendors can be assigned a dimension prior to posting their transactions, and then you can run a dimension analysis based on the Dimension Code (which in my opinion is one too-many steps to accomplish what you need...)
Let us know what you decide to do...I'm looking forward to your feedback.
Mohamad El-Sadek