SQL Server Mobile Reporting Publisher - Simple Data grid add column total

Although experienced with SSRS I am very new to SLQ Server Mobile Report Publisher. I have added a simple data grid to my report, linked it to the required dataset and now wish to show the totals for 2 columns which are currency. I can find the ability to add column totals anywhere. Tried searching for answers but to no avail. I am sure this must be very simple but could anybody assist?