I was recently dealing with something similar - I made an Extension Attribute that looks at what Wifi they are on puts that into the EA:

#!/bin/bash
# /System/Library/PrivateFrameworks/Apple80211.framework/Versions/A/Resources/airport -I | grep 'sSSID:' | sed 's/.*: //'
# http://apple.stackexchange.com/questions/191879/how-to-find-the-currently-connected-network-service-from-the-command-line
#
# Looks to see what wifi they are connected to
# 2016-11-18 gersteina1 v1.0

if [[  -e `/System/Library/PrivateFrameworks/Apple80211.framework/Versions/A/Resources/airport -I | grep 'sSSID:' | sed 's/.*: //'` ]]; then
    echo "<result>No</result>"
else
    echo "<result>`/System/Library/PrivateFrameworks/Apple80211.framework/Versions/A/Resources/airport -I | grep 'sSSID:' | sed 's/.*: //'`</result>"
fi

I then have a couple of smart groups based on the results of that EA.

gersteina1 - so when you use this EA, what do you use for your operator & value settings in criteria? I setup the EA I believe correctly (String, EA, Script and then the script you mentioned above). But not sure what to use for criteria in smart group.

Thanks for pointing me in the right direction!

I created a new Smart group that looks at the "Connected Wireless" criteria if it's not like our campus one, and not blank, then it goes into the "Wifi: Not connected to <campus ssid>" group.

So how do you squash it!

@jillhughes Take a look at this thread: Managing WiFi on macOS