The resident experts on this forum are far better qualified than I am. My own opinion is that it would be incredibly complicated to make such a trigger. As I mentioned above bets have to be matched before the desired results can be obtained and the more complicated the trigger, the less likely it is to achieve those results.
I had assumed, possibly wrongly, that the original poster was referring to in-running trading. It seems to me that that attempting to create this trigger so that it would work in very fast moving markets is an almost impossible task. I would imagine that such a trigger would be used to set desired profit and loss limits too. So, a complicated set of triggers becomes more complicated.
I am definitely ceasing trading during the next year as I intend leaving the UK. Now may be the time for me to write what I have been wanting to write for about seven years but haven't done so for fear of causing offence. Like everybody else I fell into the trap that I could churn out winning strategies with ease. I could achieve great things if only the software did what I wanted. I learned a long time ago that this was not true.
In order to trade successfully the following steps should be undertaken in order :
Step One
Study the markets, understand them, and learn the essentials of trading. Realise that markets move swiftly and that this state of flux ensures that precise calculations are rarely possible. By the time calculations are made, the market has changed ! Many bets, previously available, disappear in an instant and this screws things up in fine style.
Step Two
Learn how to use the software and appreciate its limitations. It is a tool, not a magic wand.
Step Three
When you have done steps one and two you can start thinking about strategies. To come up with strategies without completing steps one and two is a waste of your time.
No offence intended. I've contributed to many forums and made literally thousands of posts and waited until now to write this. I did not want to discourage newcomers. Too many people come up with strategies first and then see if they are practical and it should be done the other way about.
Sadly, some leading types of trading software have added worthless features to placate the demands of a few and are now unwieldy.
Geek's Toy is easily the best non-automated software and MFP is easily the best automated software. Each does its own job brilliantly and I see little point in getting both to do each other's jobs. Just use them appropriately.