How to find out whitePixelValue when person smile?

using CvRect i am able to detect faces coordinate

detectFace(IplImage * pImg, CvHaarClassifierCascade * pCascade, CvMemStorage * pStorage)

But my problem is How to find out whitePixelValue when person smile ?

And what Smile offset is appropriate ? 150 value is accurate ?

Smile haarcascade wont work at all. Need to do something with logic only with white pixels

Please help!!!

Update: I think my bounty going to be waste.. didn't get expert response on this thread. I was looking for algorithm :(