Text Entry Character Limit

Our LMS will only report data on text-entry questions if there are less than 250 characters entered. Is there a way to count the characters in the text box and have a message pop up that tells them they are over the limit when they hit Submit? 

Using triggers and variables, I can have a message pop up when they originally go over the character limit, but then I can't adjust it to know when they go back down to under 250 characters. 

Any help with this would be greatly appreciated!