I'm working with MATLAB GUI.

When I'm trying to access the variable which was defined with the push button, it is not defined in the pop up menu. The variables; it should be set 'global', so it is defined in the whole program. And I can use it in any callback.

Do you guys have any idea of how to make the variables 'global'? 

Answers: 

Wherever a global variable is going to be accessed in your code (say, different script files, functions etc.), it should be declared as such: global globalVariable;. Eg.: 

function myGUI_OpeningFcn(hObject, eventdata, handles, varargin)
    global myGlobalVar;
    myGlobalVar = [...]
    [...]
end

function btnWriteFile_Callback(hObject, eventdata, handles)
    global myGlobalVar;
    if myGlobalVar [...]
    [...]
end

Notice that in both functions the variable is declared as global in order for them to access it.