As the comments suggested, you can pass the entire handles structure at once:
function refresh_data(handles)
temp = get(handles.edittext1, 'String')
% convert temp to number, process, convert back to string
set(handles.statictext1, 'String', temp)
end
Since you're doing a bunch of these, you can loop it using Matlab's dynamic field names:
for k = 1:20
box_to_get = ['edittext' k];
box_to_set = ['statictext' k];
temp = get(handles.(box_to_get), 'String');
% processing
set(handles.(box_to_set), 'String', temp);
end
See http://www.mathworks.com/help/matlab/matlab_prog/generate-field-names-from-variables.html for more information.