This is my function to gather data fro m a listbox and save to workspace.

h_push_listbox_call.m

function h_push_listbox_call(h_push_selectws, eventdata, h_list_watersheds)
% Callback for pushbutton related to listbox and display box.

%% NOTE!! To get this to work you must set up the function inputs as 
% (the handle to the object you want, eventdata <-- exactly this!!!, and the object you are pulling from)

% handle is the object 
% just put eventdata, always empty
% handles is the structure you are getting the information from. you can have multiple ones but don't specify the fields.
    
    % The variable 'response' is assigned to the parameter of 'value' for the watershed listbox
    response = get(h_list_watersheds.list,'value');

    % in the command prompt, the response is displayed for our interest
    disp(h_list_watersheds.lookup{response}); 

    % a dummy variable 'a' is assigned to the response
    a = (h_list_watersheds.lookup{response});
    
    % the parameter of 'userdata' in h_push_selectws button is assigned to a
    set(h_push_selectws,'UserData',a);

    % in the base workspace, a variable named 'selectedwatershed' is given a
    assignin('base','selectedwatershed',a);

    uiresume(gcbf);