datediff ("N",
(Datetime(year(Minimum ({@Date Time}, {Billing_Cycle_Process_Tag_File.DocumentOrderInvoiceE})),
          Month(Minimum ({@Date Time}, {Billing_Cycle_Process_Tag_File.DocumentOrderInvoiceE})),
          Day(Minimum ({@Date Time}, {Billing_Cycle_Process_Tag_File.DocumentOrderInvoiceE})),
          Hour(Minimum ({@Date Time}, {Billing_Cycle_Process_Tag_File.DocumentOrderInvoiceE})),
          Minute(Minimum ({@Date Time}, {Billing_Cycle_Process_Tag_File.DocumentOrderInvoiceE})),
          Second(Minimum ({@Date Time}, {Billing_Cycle_Process_Tag_File.DocumentOrderInvoiceE})))),
(Datetime(year(Maximum ({@Date Time}, {Billing_Cycle_Process_Tag_File.DocumentOrderInvoiceE})),
          Month(maximum ({@Date Time}, {Billing_Cycle_Process_Tag_File.DocumentOrderInvoiceE})),
          Day(Maximum ({@Date Time}, {Billing_Cycle_Process_Tag_File.DocumentOrderInvoiceE})),
          Hour(Maximum ({@Date Time}, {Billing_Cycle_Process_Tag_File.DocumentOrderInvoiceE})),
          Minute(Maximum ({@Date Time}, {Billing_Cycle_Process_Tag_File.DocumentOrderInvoiceE})),
          Second(Maximum ({@Date Time}, {Billing_Cycle_Process_Tag_File.DocumentOrderInvoiceE})))))

 

Then I took the result and divided it by 60 to get hours

 

Now I need to get the median of the difference per group.  I have a running total to get the group total. I can also do an average but when I try to do a median it says the field can not be summarized.