Hello!
Many apologies for the delay.
I am attaching your triggers. I didn't quite understand what you mean by "market order", I assumed it was from the lowest priced selection to the highest-priced one (i.e. from favourite to worst underdog).
Also, I had to change your conditions a bit, because just any race where there top favourites form an underound would fit your criterion if the liability is unlimited:
The bets however will only be placed if the potential profit on that race is at least x% of the money that I have set to be returned.
So I set a fixed liability and stipulated that the potential profit is at least x% of that liability. If you have additional questions/remarks on this, please let me know.
Do not forget to try the trigger in Test Mode first.