Hello there.
I've worked Microsoft Dynamics GP from version 7 to version 10.
I made several excel pivot tables, (Customers, sales Orders, Inventory, etc) For example, I remember that the Customer table is RM00101 and Inventory table is IV00101 as you can see in the link you sent.
Anyway, The best way is making a View in the database (A query with the info you want) then, create an ODBC source on each PC (pointing to your Sql Server), and finally, connecting your Excel file through this ODBC to the Sql View and make the pivot table.
I could help you, but I do not remember the exact structure of your database, So, I should have some connection to your server (TeamViewer could help) but i understand it is a security issue.