title: jQuery validation trigger error message
body: <p>I have a kinda wierd problem. I want to trigger a jquery-valdation errormessage on an element even thou it's valid.</p>
  
  <p>Scenario:
  I have a large form. One of the inputs is for PersonalId. It's optional to enter that PersonalId. 
  Beside that input i have a normal button (not the submit-button). If you click on that (fetching information from ajax) and the PersonalId field is empty i want to trigger that Error-message.</p>
  
  <p>Is that possible with jQuery Validate or do i need to create my own function?</p>