Calculate a rolling average over columns

Please see the attached example. Each row represents weekly unit sold for a specific SKU we sell (not in the example). I need to get a rolling 12 week average every time a new week is not 0.

In this example =AVERAGE(J4:U4) results in 932 which is great but when column V is updated with a values > 0 then we need the average to roll to columns K thru V for each row. This needs to occur for each of the 52 weeks.


Tried incorporating OFFSET in the AVERAGE calculation but can't get this to work. HELP!!!!