How to detect start of transition from Home mode to another mode

I am pretty new to Vera. I am using it for security only (Veraplus, door/window/motion sensors etc). I used to have Iris by Lowes but they are closing down that business (I liked it just fine). I have created a few scenes and written some fairly simple luup programs in my scenes. In my setup, I have set My Modes page so there is a 90 second delay before changing from home to any other mode.

I would like to detect when I am in this 90 second delay period (i.e, transitioning from Home to Away) so I can (a) run some code to confirm all windows/doors are closed and (b) send out some beeps using some device as the arming progresses.

Is there a way to detect this pre-armed state?