function rooster(url){
   url = "http://www.tecamsterdam.nl/roosters/standaard/gpuntis_roosters.php?pag=" +url;
   window.open(url,"rooster", "width=750,height=450,toolbar=0,menubar=1,status=1,location=1,resizable=1,scrollbars=1,screenX=0,screenY=0,left=0,top=0");
}