Behaviour.register({ '#CopyContentFromID_SubsiteID select' : { initialize: function() { var treeField = $('TreeDropdownField_Form_EditForm_CopyContentFromID'); if(!treeField) return false; treeField.subsiteID = this.value; }, onchange: function() { var treeField = $('TreeDropdownField_Form_EditForm_CopyContentFromID'); if(!treeField) return false; treeField.subsiteID = this.value; treeField.refresh(); } } });