that seems like it'd be pretty simple.
create a state that chooses a random value from 1 to (width of screen) and create it at the appropriate vector.
so, say you have it creating random along the Y vector, you could "create object" with a position set to the proper vector. so, random number (let's say = 25,) create a vector3 (with the Y set to the random number but the X and Z at whatever height/depth you need) and spawn an object at the newly created vector... repeat as necessary.
not sure the finer points of this but that's where you can experiment.