I'm interested in creating a People Search query string url so that for a given property, the search will return only those users that have any value in a specific field.

For instance, I have a text field "Employee ID". Each employe has a four char string id. However, some users of the system (consultants, admin accounts) have "Employee ID" that is empty.

Is there any query string sytax that will allow me to return those users with a value in the field (any value) and exclude those that are empty?