How to create a load button in GUI manipulate the data?

Hi everyone!

This is the first time when I use GUI in matlab. I have to create a load button in which I upload my .txt file which has 3 colums with numbers. I managed to create the buttons and to open the file, but when when the file is selected, the data is not loaded into Matlab. Can you give me any suggestion? How can I transfer the data from the button to the workplace and how can I manipulate those colums?

Thanks in advance!

This is the code used:

[filename,pathname]=uigetfile('*.txt','Select Data File 1');
fullpathname =strcat(pathname,filename);
handles.data = load(fullpathname);
 guidata(hObject,handles);