Sap Logon Load Balancing Configuration

Hi,

In my production system landscape in R3 I've one CI+DB Server and 3 Application Servers. I've got around 1000 users who login into R3. Currently the users are putting the individual IPs of the application servers and accessing SAP, I want to ensure that all the application servers are used to the maximum and are evenly balanced with the user load. The users are not evenly distributed geographically. I want to make one logon group so that if any application server has a hardware failure it can be removed, rectified and added to the group without the end user knowing about it.

How do I do the configuration for the sap logon load balancing. What is the best way to go about getting this task done.

any inputs on this would be appreciated

Regards

Alfred