function SoNumero(e) {
	var nav4 = window.Event ? true : false;
	if(nav4) {
		var whichCode = e.which;
	} else {
		var whichCode = e.keyCode;
	}
	if (whichCode < 48 || whichCode > 57) {
		if(nav4 && whichCode == 8) {
			return true;
		} else {
			return false;
		}	
	} else {	
		return true;
	}
}