Validate - Allow only 1 Wildcard Character in Input

Validate - Allow only 1 Wildcard Character in Input

Apologies if this has already been answered (I did search 1st!)
 
I have a search form which has simple validation on a form input field.  I have restricted it to a minimum of 3 characters but need only one of them to be a wildcard.
 
I'm using a "%" as a wildcard and therefore "ab%" is valid but "%%%" and "a%%" etc. are not.
 
Any help is GREATLY appreciated!
 
My current code is :
 
$(document).ready(function(){
 $("#form1").validate({
    rules: {
       c: {
        required: true,
         minlength: 3
        }
      }
 });







});