function mouseover_func(button, div_id){
var button = "url(" + button + "_grijs.png)";
var div_object = document.getElementById(div_id);
div_object.style.backgroundImage=button;
}

function mouseout_func(button, div_id){
var button = "url(" + button + ".png)";
var div_object = document.getElementById(div_id);
div_object.style.backgroundImage=button;
}