Check out group-alias, group-url and group-lock features.
You can provide group-specific URL for each group, check also how group-alias affects group availability.
Finally group-lock locks users to particular group.
Some reading:
http://www.cisco.com/c/en/us/support/docs/security/ios-easy-vpn/117634-configure-asa-00.html
http://www.cisco.com/c/en/us/support/docs/security/asa-5500-x-series-next-generation-firewalls/98580-enable-group-dropdown.html