title: Get list of items in one list that are not in another
body: <p>I have two comma separated lists, the first is a list of possible values, and the second is a list of "selected" values. I need to create a list of all of the items in the first list that do not exists in the second list.</p>
  
  <p>I could just split the first list into an array and use a "for" to go through the list using a string_pos to see if the first list item is contained in the second, but I'm wondering if there is a more efficient way to accomplish this.</p>
  
  <p>Thanks!!</p>