Sure. It would require javascript to hide or show a Custom HTML field that contains a Warning Text (.warningText class).

Create a hidden field (.valueReturned class) that saves the value when hidden. Fill that hidden field with a value from your lookup table. Lookup the email address of the person filling out the form and maybe fill this field with their name or something. 

Show the warningText field when the hidden field is not empty.

$(document).ready (function () {

      $('.Submit').hide();
      $('.warningText').hide();

      $('.valueReturned input').change(hideWarningText);


      function hideWarningText() {
            var valueReturned = $('.valueReturned input').val();
            if (valueReturned != '') {
                  $('.Submit').hide();
                  $('.warningText').show();
            } else {
                  $('.Submit').show();
                  $('.warningText').hide();
        } //close else
      } //close function
}); //close docReady

I did not test this code. Just threw it together. It should give you an idea of what you'll need to do.

I currently ask the question "Is this your first submittal" and they manually answer yes or no.  If no, the whole form hides (with the exception of program overview info which contains a blurb about only submitting one entry etc).  If yes, they can proceed. 

I was hoping there was a way, with the lookup to answer the question for them, but don't see my radio button as something that can be autofilled if the last name and first name match on the lookup.

We are using 10.4.