function counterUpdate(opt_countedTextBox, opt_countBody, opt_maxSize) {
var countedTextBox = opt_countedTextBox ? opt_countedTextBox : "mensagem";
var countBody = opt_countBody ? opt_countBody : "countBody";
var maxSize = opt_maxSize ? opt_maxSize : 1024;

var field = document.getElementById(countedTextBox);

if (field && field.value.length >= maxSize) {
field.value = field.value.substring(0, maxSize);
}
var txtField = document.getElementById(countBody);
if (txtField) {
txtField.innerHTML = field.value.length;
}
}