Hi Dr. Zanusso,
you can create input objects (use right click on your current sheet). In the dailog you can create the necessary variable (and an intial input, if you like). I build a little application to show you a first direction. Look into the expression of the two (blue) text objects to get an idea how to work with dates. i.e. the "networkdays(vDate1,vDate2)"
For more details refer to your online-help/manual.
Take a glance at my app.
Third question: Don't you have any input data to load. I did load two exam fields directly.To compare i.e. amount of orders I suggest you to create a chart object.
date compare.qvw 118.8 K