okay = new Image ();
okay.src = 'gfx/goed.gif';
not_okay = new Image ();
not_okay.src = 'gfx/fout.gif';

// controle of veld is ingevuld
function check( field, image ) 
{
	if( field !== "" ) 
	{
		eval ("document.getElementById('img_" + image + "').src = okay.src");
	}
	else 
	{
		eval ("document.getElementById('img_" + image + "').src = not_okay.src");
	}
}