Arming ADT alarm after everyone has left

I just bought the ADT Home Security Starter Kit that works with SmartThings, and have it all set up. I am very happy so far with this, and look to keep building out my new smart home. I am new to SmartThings, and have been getting myself acquainted with the forums here. Thank you all for your input on this forum, as I have been able to find some useful tips.

I do have one question/automation that I would like to setup:

I’d like to have the alarm system automatically set to arm (away) when everyone leaves the house.

I’ve tried to create this in the Goodbye routine, as well as SmartApps, but I have been unsuccessful,

Any help or advice would be appreciated.

Thank you

In this thread there is some discussion on how you can use webcore to do this: