OS X :: Work Days Left Excluding Weekends / Holidays

I want an app - or something like that - that can tell me how many work days that are left from today to an other specified date. I found a little app called Days Left, but that only works with the total amount of days and doesn't exclude weekends and holidays. I've successfully made a spreadsheet in both Excel and Numbers (to check which was better) that can do this for me. With Quick Look it's almost like the little app that I wanted. The problem is, that I don't want to open up the spreadsheet every day, so Excel or Numbers can refresh the =Today() formula and thus give me the right date in Quick Look. Are there any ways I can have the spreadsheet update when Quick Looking it or in any other way without having to start up the program itself every time?