function update() {
			var mask, trs, tr, tds, grp, cls, i, j, n, m, bor;
			mask = 1
				+ (document.filterform.group1.checked ? parseInt(document.filterform.group1.value) : 0)
				+ (document.filterform.group2.checked ? parseInt(document.filterform.group2.value) : 0)
				+ (document.filterform.group3.checked ? parseInt(document.filterform.group3.value) : 0)
				+ (document.filterform.group4.checked ? parseInt(document.filterform.group4.value) : 0);
			trs = document.getElementsByTagName('tr');
			n = trs.length;
			for (i = 0; i < n; i++) {
				tr = trs[i];
				if (tr.className.indexOf('dates') >= 0) {
					grp = parseInt(tr.id.substring(tr.id.indexOf('_')+1));
					cls = (grp & mask ? 'st1' : 'st2');
					if (tr.className.indexOf('border') >= 0)
						cls += ' border';
					tr.className = 'dates ' + cls;
					tds = tr.childNodes;
					m = tds.length;
					for (j = 0; j < m; j++) {
						tds[j].className = cls;
					}
				}
			}
		}