hello and thank you in advance for anyone who can successfully help me accomplish my goal

what I want to accomplish is this in an excel table I want the formula :

A1 + B1 = B1

where A1 is a changing number, in my case a daily sales number
and B1 is a running total of each days sales for a week, month or year

so if :
Day 1 of week 1 = 3 (cell A1) then week 1 = 3 (cell B1)
and if
Day 2 of week 1 = 2 (cell A1) then week 1 = 5 (cell B1 + previous total in B1)
and if
Day 3 of week 1 = 4 (cell A1) then week 1 = 9 (cell B1 + previous total in B1)

and so on, and I want it to be accomplished in as few cells as possible, just 2 would be ideal

this would also go for monthly and yearly sales totals which would also update their totals using the variable in Cell A1.

and if your really energetic maybe you can show me how to automatically cycle the formula at the end of week and month

thanks again