How to write scratch condition on matched back bet?

Hi ,

I want to scratch my back bet (other words lay at same price as backed) if the following:
The liquidity at the price I backed at decreases 50% or more and the Liquidity increases lay side increases 50% or more.

As a backup rule if the price does move against me (without an increase in waiting money at the best price) then it will exit my position at the best possible price available.