var frame=0;
var preview_interval;
var prev_frame;
var tmp;
var curleft;
var curtop;

function intervalWrapper(key)
{
    return setInterval("change_preview('"+key+"')",500);
}

function change_preview(key)
{        
    document.getElementById("preview_"+key+"_"+prev_frame).style.display="none";
    document.getElementById("preview_"+key+"_"+frame).style.display="block";
    
    frame++;
    if (frame==10) frame=0;
    if (frame==0) prev_frame=9;
    else prev_frame=frame-1;
}