advice and consultancy required for a software program for multiple offices with a central database stored remotely

we have developed a VB software program that up to now has worked on local networks in small offices with an Access database and 4 or 5 users. We now need to set up this software in 5 or 6 offices with over 20 users with a shared database hosted remotely. We need to get advice from someone who can let us know the best way to approach this. We have already migrated the database to SQL Server and that is working well. The main option that we are looking at is a VPN and we have done some testing of this. We have found with one user it is performing well when the database is stored remotely and the resources are stored locally. However, so far we are getting extremely bad results when we have more than one user. The time that it takes to carry out a task with more than user is so bad that it is absolutely prohibitive. Our bandwidth is good at 2Mbs down and 512Kbs up. Pinging to the remote server is averaging 43ms. We need someone who has advised or who has been involved in successfully implementing systems like this in the past to give us 2 to 4 hours advice on a consultancy basis to help us find the best solution to to deliver this service. We can provide statistics on the performance of local versus remote versus one user versus multi users versus limited remote resources versus all remote resources if requested. Please only bid for this project if you have a lot of experience in this area and you already have a high rating on GAF.