Sure, just build a new filename instead of reusing the old one...use pieces of the old if desired, of course. You just have to have some way to decide what the new piece(s) are to be. Here I just stored them as an array internally; you may want something more clever...knock your socks off in that regard. :)
stuff={'maxtemp';'mintemp'}; % the new pieces for file names
...
for i=1:length(sourcefiles)
...
[p,n,e]=fileparts(sourcefiles(1).name); % path,name,extension
% do what to get max temp's and ready to write
outname=strcat(n, stuff(1), e);
xlswrite(outname,biggarr);
% now get min temp's and ready to write
outname=strcat(n, stuff(2), e);
xlswrite(outname,biggarr);
...
This will duplicate your sample cases above for each pass thru the loop on multiple files.
As always, "salt to suit..." :)
