I define a variable (menu option view --> variables --> New) - the variable creation screen allows you to select sum as the calculation type (right side of box). You will need to define the variable as an Integer, Double, or BigDecimal as appropriate. Reset type defines when the variable gets reset (when the grouping changes or for the entire report). Say you have a report that needs a sum of transactions for cashiers - create a cashier group (which gives you the bands for cashier header and footer), then create a variable that does a sum reset by group - group is cashier). Menu screens in 1.2.6 for creating a group is View --> Report Groups. For Variables it is View --> variables.