Non-pure node (once with exec pins) pins states clear or end of node continuity (end of scope), so in your case after “Bind to Event to OnClicked” the scopes end and state of “Return Value” you use to get widget reference is cleared and can not be reused or else retrigger the node (which in your case there no point of doing that).
You forgot about most basic thing you can do… to keep the reference of object you made in variable to control it later ;]