Custom module and custom list view - Popup

[JohnMaverick]

So I designed custom list view with two fields. I want Third field to be entered with use of popup. Here I hit hard part as non of mine ideas works. Basically I am storing popup in some var which shall be passed to this field upon hitting save button adjacent to those two fields laying below popup. That is not working. May anyone gimme some light on what should be done to make this basic thing working? Sort of quick edit will not work as I need to save record ONLY when popup is closed
Appreciate pointers