Create the annotation once, and then only change the string property inside the loop.
figure(1)
txt='';
h_annot=annotation('textbox',[.9 .5 .1 .2],'String',txt,'EdgeColor','none');
for steps=1:5
step_number=steps;
txt = sprintf('Steps number: %d units',step_number);
set(h_annot,'String',txt)
drawnow%force graphics update, pause(0.001) will work as well
for k=1:1e6
1+1;%have some calculation to simulate your actual processing time
end
end
close(1)
