var checkflag = "false";
function checkall(objForm) {
	if (checkflag == "false") {
		for(i = 0; i < objForm.elements.length; i++) {
			if(objForm.elements[i].name != "availability") {
				objForm.elements[i].checked = true;
			}
		}
		checkflag = "true";
		return "Uncheck all";
	} else {
		for(i = 0; i < objForm.elements.length; i++) {
			if(objForm.elements[i].name != "availability") {
				objForm.elements[i].checked = false;
			}
		}
		checkflag = "false";
		return "Check all";
	}
}