Hi, I don't use windows, but your symptoms sound like when you run system to start the xls file, you don't do it right, and it takes control and blocks the Tk GUI. Maybe you should fork before calling system, ( or whatever they do on windows). Here are a couple of links: MS Forking Blues where tye shows system (1, $prog) which may work for you. Perl Tk: opening a file in its original format