Combine 2 fields for custom urlTitle field

customUrlTItle.vtl

#set($cusFieldVarName="urlTitle")
#set($f1VarName = "coursePrefix")
#set($f2VarName = "courseNumber")

<script>

  function updateDisplayURLTitle() {
    
    // get the fields entered by the user
    var f1 = dojo.byId("${f1VarName}");
    var f2 = dojo.byId("${f2VarName}");
    
    // combine the fields
    var urlTitle = f1.value+"-"+f2.value;
    dojo.byId("display${cusFieldVarName}").innerHTML = urlTitle;
    dojo.byId("${cusFieldVarName}").value=urlTitle;
  }

  // attach this the text1 field onchange
  dojo.addOnLoad(function(){
      dojo.connect(dojo.byId("${f1VarName}"), "onchange", null, "updateDisplayURLTitle");
      dojo.connect(dojo.byId("${f2VarName}"), "onchange", null, "updateDisplayURLTitle");
    }
  );
  // populate the field on load
  dojo.addOnLoad(updateDisplayURLTitle);

</script>
<div id="display${cusFieldVarName}" style="height:20px"> </div>​