No...not the set method. I am talking about setting the collection. Do one thing, check the initialization of your table view. There you will see something like me->set_collection (lv_collection) or lr_entity->set_collection(lv_collection). That means you are updating the collection for the entity with the values.
The same can be used in our case as well. What you probably can do is,
1) Once user presses No, Set the collection's field value with the old value (in dropdown in your case).
2) Then call me->set_collection by passing the above collection.
Try out this. If you are unable to do, let me know. I will give you the code once connected to the system.
Thanks,
Faisal