Mine

var t = false; 
			var fs = document.forms['myForm'].elements['copy_list']; 
			for (var i = 0; i < fs.length; i++) { 
				if (fs[i].checked) { 
					t = true; 
					break;
					} 
				}
				if (t == false) {
					alert('You must check at least one sub-User Checkbox to copy settings to.');
					return false;
				}