Horseracing: keeping same lay price after reduction factor applied

Is there any way of ensuring an initial lay price for a horse (generally well below current odds/looking to match in-running) can be kept the same even if there is a non-runner/reduction factor applied? If laying at lowish odds a reduction factor of even a few % can make a big difference to price laid; i can sometimes do a quick check close to racetime to see if this has occurred and will change the odds manually, but not always.

I presume there is basic software/apps/bots that can do this type of thing, but i just want to set the bets well in advance then switch off the laptop. I've seen that it's possible on the purple site but the liquidity there in-running is still minimal, so is there just some key or hidden setting here that i haven't seen?

Thanks.