I have the following data.

User   Order                         Date and Time                     Qty      Time Taken in Sec

                                                                                                            (Formula Name Diff)

Mr. X   552678                       07/31/2013 05:00:00am      10

            552678                       07/31/2013 05:10:15am      25

            552678                       07/31/2013 05:12:00am      10                    720

            552690                       07/31/2013 05:15:00am      5

            552690                       07/31/2013 05:20:25am      10                    325

Mr.Y    552695                       07/31/2013 11:55:00am      50       

            552695                       07/31/2013 12:05:15pm      25                    615

Using the Min Max Sum on the field Date and Time and using the formula

DateDiff("S", Maximum ({Date and Time}, {order ),Minimum ({Date & Time}, {Order}))       I am able to get the time taken in seconds to fulfill the order at the order level. I have also placed this at the report footer.

I want to get the total time taken for all orders at the user level in seconds. I tried Sum(@Diff}, {Order})

And I am getting a message “The Field @Diff cannot be summarized.

Any help with this will be greatly appreciated. I need totals in Seconds only for each user.