need a sample code for face recognition using Neural Network (backpropagation)

Hi. I am an undergraduate student of Biomedical Engineering. For my final project, I need to know about face recognition using ANN. I know that I should use backpropagation, but I think it will be very helpful if I see a sample code of face recognition first. I will be very thankful if anybody could help me about it.

P.S. I know about "Neural Network Pattern Recongition" tool in MATLAB (nprtool), but I don't know how should I define my input for it (images of faces).