Passing value from one function to another function in the same .m file

function Check_Callback(hObject, eventdata, handles)
blah = get(handles.Option,'SelectedObject');
blah = get(blah,'String');
leaf1 = 'Parsley';
leaf2 = 'Coriander';

tf = strcmp(blah,leaf1);
tf2 = strcmp(blah,leaf2);

result1 = 'You are right, it is a parsley leaf';
result2 = 'You are right, it is a coriander leaf';
result3 = 'You are wrong, it is a parsley leaf';
result4 = 'You are wrong, it is a coriander leaf';

if (G <=  200 && tf == 1)
    set(handles.text3, 'String', result1);

else if (G > 200 && tf1 == 1)
        set(handles.text3, 'String', result2);

else if (G <=  200 && tf1 == 0)
    set(handles.text3, 'String', result3);

else if  (G > 200 && tf1 == 0)
        set(handles.text3, 'String', result4); 
    end
    end
    end
end
 set(handles.Analyze,'Enable','on') 

function Upload_Callback(hObject, eventdata, handles)
[a, b]=uigetfile ({'*.*', 'All files'});
img=imread(fullfile ([b a]));
imshow (img, 'Parent', handles.QueryImage);
set(handles.Analyze,'Enable','off');

[Stephen23]

If you are using GUIDE then use guidata. If you are sensibly writing your own code then use nested functions. Both of these are explained in the documentation:

https://www.mathworks.com/help/matlab/creating_guis/share-data-among-callbacks.html