var bm_images ;
var bm_currImage = 0;

function bm_ChangeImage(move,pic) {
    var noImages = bm_images.length;

     bm_currImage = bm_currImage + move;
     if (bm_currImage > noImages - 1) bm_currImage = 0;
     else if (bm_currImage < 0) bm_currImage = bm_images.length - 1;

     document.getElementById(pic).src = "images/" + bm_images[bm_currImage];

 }