Don't limit characters until form is submitted

The character limit is great. However, I don't want to limit the character count until the form is submitted. In effect, I'd like to show the character count and indicate the max # of characters, but let the user type in as many characters as they want; if they hit submit and their character count is above the max, only then will they get an error.

So I need to build a custom form field without the javascript character limiter, but then how do I have GF check the character count and/or display an error upon submit??