function CountTextBoxCharacters(textBox, long) {

    var maxlength = new Number(long); // Change number to your max length.
    var text = textBox.value;
    if (textBox.value.length > maxlength) {
        textBox.value = textBox.value.substring(0, maxlength);
        //alert("Only " + long + " chars are allowed");
    }
}