Calculating the average every nth cell but allowing for new columns

[Crofty92]

Hello,

I have the formula =AVERAGE(IF(MOD(COLUMN(BH7:BT7)-COLUMN(BH7),2)=0,IF(BH7:BT7>0,BH7:BT7)))

It calculates an average for the last 8 weeks, is there a way of changing it so when a new week is added i don't have to manually change the data range every time?

Thanks

[Jonmo1]

Can you attach a small sample book?
There may be an easier way.