You want to track the various Notes client installations throughout your environment. The Names and Address book Person document does track client versions but it tracks all client versions for a user in no particular order.
This is a LotusScript example of how to track each user’s current Notes client version based on the last time they opened their mail application. It is important to note that some users may share a workstation or have access to multiple workstations. Also this solution is dependent on users periodically closing and opening their mail application. This example utilizes a central database on the user’s home mail server. The database has a simple form with fields that track User Name, Current Client Version, and Machine Name.