How do I reference a handle structure instead of creating a local copy?

Hi,

I'm creating a user dialog where, depending on user selection, I'd like to populate the figure with different uicontrols. In order to make my code a bit more readable, I have created separate functions to create my uicontrols. In the example below I use a function HeightFields to create uicontrols for a specific user selection. What I would like to do is have this function create these uicontrols and update the handle structure of my figure.

However, the use of the guidata function does not update the handle structure in my main function, even if I would renew the guihandles command. So, instead I have my function generate the handle structure of the figure as an output. It works, but it's not really elegant. I have searched for an answer here and found that most likely, I'm creating a duplicate structure, rather than addressing the original one. The strange thing is that whenever I use a callback function (e.g. the TypeSelection one) rather than a regular function it does seem to work.

Would anyone be able to explain how I can reference the main handle structure instead of a copy and why the behaviour is different between a callback and other functions?

Thanks!

function y = CreateProfile
    % Create figure
    fh = figure('Name','Create Profile','NumberTitle','off',...
        'position',[400,250,500,350]);

    % Disable Menus
    set(fh,'MenuBar','none');     

    % Create content in figure
    pop_Type = uicontrol('Style','popupmenu');
    pop_Type.String = {'Peak Height', 'Peak Area','Correlation'};
    pop_Type.Position = [150, 280, 100, 40];
    pop_Type.Callback = @TypeSelection;  
    
    
    % Obtain handle structure    
     prof_handles = guihandles(fh);
    
    % Update handle structure
    prof_handles.pop_Type = pop_Type;
    guidata(fh,prof_handles);   
    
    % Create UI Controls for Peak Height
    prof_handles = HeightFields(fh);
    guidata(fh,prof_handles); 
    
    y = 0;
end

function TypeSelection(fh,~,~)
% Get handles structure
prof_handles = guidata(fh);

switch prof_handles.pop_Type.Value
    case 1 %'Peak Height'
        prof_handles = RemoveFields(fh);
        guidata(fh,prof_handles)
        prof_handles = HeightFields(fh);    
    case 2 %'Peak Area'
        prof_handles = RemoveFields(fh);
        guidata(fh,prof_handles)
        prof_handles = AreaFields(fh);
    otherwise
        prof_handles = RemoveFields(fh);
end
guidata(fh,prof_handles);
end % TypeSelection

function prof_handles = RemoveFields(fh)

% Get handles structure
prof_handles = guidata(fh);

if isfield(prof_handles,'txt_Type')
    delete(prof_handles.txt_Type)
    prof_handles = rmfield(prof_handles,'txt_Type');
end

if isfield(prof_handles,'edit_Position')
    delete(prof_handles.edit_Position)
    prof_handles = rmfield(prof_handles,'edit_Position');
end

if isfield(prof_handles,'txt_Position')
    delete(prof_handles.txt_Position)
    prof_handles = rmfield(prof_handles,'txt_Position');
end

guidata(fh,prof_handles);
end % Remove Field

function prof_handles = HeightFields(fh)
% Get handles structure
prof_handles = guidata(fh);

txt_Type = uicontrol('Style','text');
txt_Type.Position = [50 280, 100, 40];
txt_Type.String = 'Profile Type';
prof_handles.txt_Type = txt_Type;

edit_Position = uicontrol('Style','edit');
edit_Position.Position = [150 255, 100, 20];
edit_Position.String = '3000';
prof_handles.edit_Position = edit_Position;

txt_Position = uicontrol('Style','text');
txt_Position.Position = [50 230, 100, 40];
txt_Position.String = 'Peak Position';
prof_handles.txt_Position = txt_Position;

guidata(fh,prof_handles);

end % HeightFields

function prof_handles = AreaFields(fh)
% Get handles structure
prof_handles = guidata(fh);

txt_Type = uicontrol('Style','text');
txt_Type.Position = [50 280, 100, 40];
txt_Type.String = 'Profile Type';
prof_handles.txt_Type = txt_Type;

edit_Position(1) = uicontrol('Style','edit');
edit_Position(1).Position = [150 255, 100, 20];
edit_Position(1).String = '3000';

edit_Position(2) = uicontrol('Style','edit');
edit_Position(2).Position = [300 255, 100, 20];
edit_Position(2).String = '3000';
prof_handles.edit_Position = edit_Position;

txt_Position = uicontrol('Style','text');
txt_Position.Position = [50 230, 100, 40];
txt_Position.String = 'Peak Position';
prof_handles.txt_Position = txt_Position;

guidata(fh,prof_handles);

end % AreaFields