VBA - Incoice Number Generation

Here's what I'm looking for: The creation of five files: Four Word files and one Excel file... The four Word files (docs or templates) would all generate invoice numbers from the same master file (Excel). So if the Word files were named "Doc1", "Doc2", "Doc3" and "Doc4" and an invoice number in Doc2 was, say "10727" then the next invoice number to be generated would be "10728" regardless of which document it is going to or who requested it. Additionally, it would need to be possible for two users to have "Doc2" open at the same time. Preferably, to prevent accidental deletion/change, these files would be protected from being saved as their original name. One note about the sequencing requirement... it needs to be accessible to both "limited" and "computer administrator" accounts. For example, if I log in as a "computer administrator" and the invoice is 10727 and then I log on as a guest with "limited" access, the next invoice number needs to still change to 10728. When I cut and paste the VBA programming I have seen on the web, it does not correct this. It only updates the invoice number if it is done by someone with "computer administrator" access. To "create" this invoice number either one of the following two methods to generate an invoice number when inside a word document: - creating a button on the toolbar that would generate the invoice number (preferred method) or.... - creating a button in the Word document itself that would generate the invoice number. thanks!