Is the ActionScript your own work? If you know how to write a situation in AS "converting" to C2 is very easy!
After a brief look at your code, it looks like the first stanza (I like poems!) deals with the default behaviour of the turret, you can do this easily in C2 with a boolean variable as the condition for your entire event,just make a boolean variable called TurretActive.
Second stanza looks like a cooldown effect, this is also quite easy with events, simply make a variable called Cooldown that is set to a number (Let's say 3) every time the turret fires, and decrememnts by the value of 1 every time the turret fires.
Finally you've got your turret actually firing, for this you want to make sure that you have three conditionals for this event. The first is that TurretActive is set to True, the second is that Cooldown has a value less than or equal to 0.
The third conditional is the distance from the target, again this can be a boolean variable, and can draw it's values from the .distance expression, comparing your turret and target sprite. Set the bool to true if the distance is close enough (say 500?)
When all of these conditions are met, it's a simple matter of spawning a sprite with the bullet property at the angle of your target, which you can do with the angle expression.
You can add all kinds of finishing touches like rotating you turret, imagepoints and the like; if you're dealing with many targets it will be worthwhile reading up on unique IDs and sprite picking.
C2 is effectively pseudocode, if you have a good grasp of your mechanics it's an absolute joy to use.