function maxLength(field, maxChars) {
    if (field.value.length >= maxChars) {
        event.returnValue = false;
        return false;
    }
}

function maxLengthPaste(field, maxChars) {
    event.returnValue = false;
    if ((field.value.length + window.clipboardData.getData("Text").length) > maxChars) {
        return false;
    }
    event.returnValue = true;
}