Documents for QlikView related information.
This zip file (.qvw and xlsx file) exemplify a basic scenario of how you can use variables to switch the field that is used to calculate a metric across multiple objects.
Thanks for this. You can also add a tip from Rob Wunderlich to put dynamic lists into an alternative state. This means that the selecting of values in the lists does not cause the default state to rebuild its cache. Even in smaller apps you will a marked performance improvement.