function Bloqueia_Caracteres(evnt){

	if (navigator.appName.indexOf('Microsoft') != -1) {
		 clientNavigator = "IE";
	} else {
		 clientNavigator = "Other";
	}

	if (clientNavigator == "IE"){
		if (evnt.keyCode < 48 || evnt.keyCode > 57){
			return false
		}
	}else{
		if ((evnt.charCode < 48 || evnt.charCode > 57) && evnt.keyCode == 0){
			return false
		}
	}
}