The easiest way to allow a user to specify the unit of measure or similar thing is to have the user select a value for a variable through an input box or select a value for a special field that is set up for the purpose. See this article for an idea how to do it: http://qlikviewmaven.blogspot.com/2010/06/user-option-done-as-field-selection.html
Another possibilities are to show or hide expression columns based on a user selection so the expressions that are shown are based on the users choice.
Something that allows a lot of flexibility in the appearance of a chart is to have two or more charts that occupy the same space on the sheet. Then, specify a show condition for each chart so that only one of them appears at a time. Make the show expression depend on a variable value or field value or day of the week or user name, etc. Then one chart might show dollar value and a different chart might show tons of product and another chart might show consumption of pollution credits, etc. A similar thing is to have two or more sheets/tabs set up with a show condition so that only one of the sheets is visible at a time. That way the expessions and charts are more simple and the special show expression only exists in the sheet properties.
