Sustainability of excel (VBA) - SQL server 2008 App for large number of users

Hi,
First of all i don't see any problem in scaling out your application from 200 users to 2000 users. But considering that it is excel and vpn, please check:
1. Network bandwidth. As you are using a lot of excel rows to import/export, it may be a hinderance when working across the globe on VPN. Though, you can not do much in this aspect.
2. Current Architecture. If you can get the current locking/blocking status with 200 users then you can anticipate the locking/blocking that may cause in 2000 users. This might gives you some idea about changing the architecture of current system.

If you don't put something like blue-moon benefitis, no-body would allow to re-write the application. But still if you get some chance, my idea is to go with ASPX~SQL or VB~SQL. Being the microsoft technology, much of your current VBA code can easily be re-written in the new technology.

Thanks for the information. In addition to above any tuning required on database side (which is hosted on a poly server) ?

My justification for aspx-sql over vba-sql would be that a web app would use the server to process the calculations over vba front end which depends more on user's local system (which usually results in slow performance if sys is installed with low memory). Would you agree on this ?