function roll(img_name, img_src) {
	document[img_name].src = img_src;
}
function toggle(id) { 
	var tr = document.getElementById(id); 
if (tr==null) { 
return; 
} 	
	var bExpand = tr.style.display == ''; tr.style.display = (bExpand ? 'none' : ''); 
} 
function changeimage(id, sMinus, sPlus) { 	
	var img = document.getElementById(id); 
if (img!=null) { 
	var bExpand = img.src.indexOf(sPlus) >= 0; 
if (!bExpand) 
	img.src = sPlus; 
else 
	img.src = sMinus;
} 
}