var currentImage = 0;
var totalImages = 7;
var viewSize = 3;

function moveToPrevious()
{
  if(currentImage > 0)
  {
    new Effect.Move('imageBoxInside', { x: 0, y: 130, transition: Effect.Transitions.sinoidal });
    currentImage--;
  }
}

function moveToNext()
{
  if(currentImage < totalImages-viewSize)
  {
    new Effect.Move('imageBoxInside', { x: 0, y: -130, transition: Effect.Transitions.sinoidal });
    currentImage++;
  }
}