var img = [];
img.push('http://www.djmarkknight.com/wp-content/themes/markknight/images/bio/img1-large.jpg* ');
img.push('http://www.djmarkknight.com/wp-content/themes/markknight/images/bio/img2-large.jpg* ');
img.push('http://www.djmarkknight.com/wp-content/themes/markknight/images/bio/img3-large.jpg* ');

function update(which){
document['PhotoBig'].src=img[which].split('* ')[0];
document.getElementById('caption').innerHTML = img[which].split('* ')[1];
}