sort by date and quantity

[bestgroup]

I created input forms in which each user enters their name and a quantity, every day. In edit view I can sort the view by date. Within the date I can see all the users to whom I have associated (through group aggregate) the sum of the quantities for each single day. I would like this view, within each date, to be sorted from largest to smallest quantity. The sorting should be: by date of the day, then by username from the one who produced the most to the one who produced the least. It's possible? Thank you