VPN geolocation with RADIUS

Hello,

For a professional environment, I need to investigate the possibility to add geolocation capabilities to our VPN infrastructure, in order to provide location-dependent access rights.

To summarise, the goal would be to interface the VPN concentrator to a RADIUS server, configured to look in an IP address and country database.

My question is: do you know or use a RADIUS server providing that kind of application and with the following characteristics:
- Runs on Windows platforms
- Allows authentication through certificates
- Is flexible enough to search that geolocation database and trigger actions related to the result

Thanks in advance!