I bet you can find this in your taiji. It is in xiao baji and an interesting way to counter a shoulder kao.
http://www.youtube.com/watch?v=2ddjK4aK ... re=related
This technique is called Dao Gou in Chinese becasue the foot hooks your opponents leg while moving along an arc similar to that of a Chinese broadsword... thats my best guess anyway. There are many counters to this technique - as with all techniques - and interestingly you can use Dao Gou to counter Dao Gou!
So, to increase your chances of success remember: practice the Dao Gou footwork frequently control your opponents balance by pulling in and downward in an arc in a horizontal plane the footwork stays pretty much the same whatever you do with your hands, but you need to be coordinated and well timed