How do you create a Acrobat pop up message when character limit is reached?

Hello! I have a character limit on a fillable form in Adobe Acrobat. However, I want to create a pop up to appear when the user reaches the limit that basically says "You've reached the maximum word count for this section".

My goal is to make it obvious that the user has reached the maximum, since I'm finding a lot of the forms are coming back with cut off sentences, despite an accepted word count written on the page's directions. People didn't realize that their typing was no longer being accepted, or they just copy & pasted some text without realizing that the last chunk did not paste.