function expand_collapse(obj, imgobj) {
	var im=document.getElementById(imgobj);
	var el = document.getElementById(obj);
	//alert (obj+' id '+el);
	if ( el.style.display == 'none' ) {
		//entonces expanda
		el.style.display = 'block';
		im.src='/images/arrow_collapse.gif';
	} else {
		if (el.style.display == 'block') {
			//entonces collapsa
			el.style.display = 'none';
			im.src='/images/arrow_expand.gif';
		}
	
	}
	
}