function MudaCampo(f){
	if(f.value.length==f.maxLength){
  	for(var i=0;i<f.form.length;i++){
    	if(f.form[i]==f&&f.form[i+1]){f.form[i+1].focus();break}
		}
	}
}

function isNum( caractere ){
 	var strValidos = "0123456789"
	if ( strValidos.indexOf( caractere ) == -1 )
	return false;
	return true;
} 

function validaTecla(campo, event){
	var BACKSPACE= 8;
	var key;
	var tecla;
	CheckTAB=false;
	if(navigator.appName.indexOf("Netscape")!= -1)
	tecla= event.which;
	else
	tecla= event.keyCode;
	key = String.fromCharCode( tecla);
//	alert( 'key: ' + tecla + ' -> campo: ' + campo.value);
	if ( tecla == 13 )
	return false;
	if ( tecla == 0 && !window.event )
	return true;
	if ( tecla == BACKSPACE )
	return true;
	return ( isNum(key));
}