To display data that is a calculated value, you need to create a formula field and place that formula field on the report. For example, if the database only stores the order dates and ship dates for orders but you need to display the number of days it takes to ship the order, you must create a formula field that will calculate the number of days between ordering and shipping. This is just one example of the use of formula fields. For an introduction to formulas, see
Using Formulas.