Hello!
If you are talking specifically about SP betting whereby you set the liability of your future bet (for laying) or the size of your future bet (for backing), then you can set the worst limit of the price you want to take. E.g. if you set the trigger to "back at SP" and then set "Price" to 10.0, this means the bet can be matched at 10.0 or higher, and if the SP price is 9.0, the bet will be discarded.
Similarly, if you "lay at SP" and set "Price" to 10.0, this means the bet can be matched at 10.0 or lower.
All that said, SP bets can only be placed before the market turns In-Play (i.e. in Idle state).
Hope this helps.