var SelectedImage = "";
    function SetImage( _Image )
    {
        var Image = _Image;
        
        if (SelectedImage != Image)
        {
            var NewSrc = Image.src;
                NewSrc = NewSrc.replace(".jpg","-big.jpg");
                document.getElementById('BigImage').src = NewSrc;
            
                Image.className = "SmallImageSelected";
                
                if (SelectedImage != "")
                    SelectedImage.className = "SmallImage";
                    
                SelectedImage = Image;
         }
    }