Oh it's possible alright. <img src="smileys/smiley2.gif" border="0" align="middle" />
You'd need to have two copies of the sprite and then make use of the blend modes (check out the example capx for that) to make part of one sprite invisible and the corresponding part of the other sprite invisible. It gets trickier if you want to make the cut at an angle or off-center, but definitely doable.
I can't make an example right now because I'm on my phone, but let me know if you need one later on.