First time I've posted and very new to automation, so please be gentle on me

First of all, can I say helpful this forum and some of the automations you share are brilliant and ery generous.
So I am hoping you can help me please?
I have put together a very simple automation which backa a horse at pre-off, and then greens up in play for 20%. I was wondering how I may add a stop loss so that should it go 20% against me, the bot stops and greens up for the loss. I'm sure it's very simple but so am I

Many thanks.