Backing in the Place market based on price change in the Win market
At 30 sec before the start of the race find a runner whose chances for a win grew up by at least 2.0 in the win market. Then back on this runner in the place market.
The chances for a win are calculated according to this formula:
chances = 100/price
Therefore, if a runner was priced 4.8 and then its price dropped to 4.0, its chances have grown by (100/4.0 - 100/4.8) = 4.16. Pay attention that this figure is not the same as the percentage of the price change. I.e. the price change in this case is (4.0 - 4.8)/4.0 = -20%.
You will find several constants in the file which will help you to tweak the trigger. You can set the time before the start, the maximum price of the selection to back on, the time interval and the value by which the chances must grow.