I would first try creating a sprite just for overlap detection. Just change the size and rotation of that sprite at runtime between the 2 barriers, then check if your player disc is overlapping that sprite. That sprite would be invisible in the real game though.
If the disc is going at high speeds then you could move the player's disc with the Bullet behavior and enable stepping mode so you can do more fine grained overlap tests.
If you need the disc to only be able to cross in a certain direction, like crossing over the finish line in a racing game, then that gets a lot more complicated, but still doable. It would require you to model the sprite positions as vectors and compute the dot product. Let me know if you need this and I can attempt to elaborate on it.