Search VisionBib for an algorithm:http://iris.usc.edu/Vision-Notes/bibliography/contents.html. We don't recommend an algorithm when they are so complicated. There are lots of published papers oneye location on the face , and oneye tracking (where in the scene that the eyes are looking), so look them over, pick one that looks promising, and code it up. Come back if you have questions about syntax, error messages, etc. that areMATLAB-related.
If you have the Computer Vision System Toolbox, you may want to try the vision.CascadeObjectDetector with one of the 'EyePairSmall' or 'EyePairBig' classification models. Here's some example code for face detection and tracking that you may be able to adapt to your use case: