If you have some "onee-chan!" sound clip, set that as your combobreak.wav.
If you don't, but know of an anime that does, get some episodes playing, try and find that delicious sound bite, and then use audio editing software like Audacity, with your Recording Source as "Stereo Mix". You'll need to set your volume a bit high though. Here's a guide to do that.
Someone around here might have a sound clip though, or maybe Google Fu can kick in too. Good luck!