A steal is when someone is in the button, small blind, or cutoff position, hasn't faced a caller or raiser yet, and then makes an open raise. Stats for this are very important so it is necessary to be very flexible with this. The first thing we need to do is rule out limpers. The reason for that is that if there are limpers, it's no longer a steal but rather an isolation.
The next thing is to specify the steal itself
It is a matter of preference if you want to use pre-selected positions as was done in this example or distance from the button. The problem with distance from the button would be that in very small game sizes, the first raiser might get counted as a steal even if he was first to act. Using presets prevents that.
Now to make the definition more interesting, we will convert it into a "steals hero's big blind" definition. What we need to do is add an action called "HeroPostBig" to the top. Here we just specify a few things and the final screen looks like this:
You can see they need to be in order here as well. If you wanted to make a definition where someone steals hero's small blind or big blind, then you'd make a second sequence, identical to the first, except for the fact that the first action would have hero posting the small blind instead of the big blind.
Here is the completed definition (right click->save as):
StealHeroBigBlind.xml