If you only accept office mode you can use the assigned network for a alert rule.
Lets say you have assigned 192.168.10.0/24 as the office mode pool you can make a rule like the following.
Code:
source | destination | VPN | service | action | track
------------------|-------------|-------------|---------|------------------
SR-Users@any | SRV-GRP1 |RemoteAccess | http | accept | log
Net_192.168.10-24 | any |RemoteAccess | any | reject | mail