Excel 2007 :: Get Two Cells To Be Used To Adjust Other Cells On Same Sheet Repeated Times

I am trying to get two cells to be used to adjust other cells on the same sheet repeated times.

In a inventory sheet I have 5 columns as such , A1 previous balance, B1 Qty received, C1 qty on hand, D1 last cost, E1 current avg cost What I want, is to be able to enter my weekly received items in the B1 Qty received and the new cost in D1 Last cost cells and have them calculate my current average E1 and update my qty on hand C1 total. This in itself is not the biggest challenge. I was asking if there is a way that after the E1 current average cost and C1 qty on hand are updated by that formula, that the next time I enter a new B1 qty received and new cost in D1 Last cost cell they will update again basically without changing the earlier calculations achieved .

Example: Today I have item X with a A1 previous balance of 10 , with a D1 last cost of $1, and E1 current avg cost $1

I want to receive B1 10 more today at $.50 D1 last cost, which ideally would end up showing

A1 previous 10 (or 20 if adding) , C1 Qty on hand 20, D1 Last cost .5, E1 current avg $.75

Next week I want to receive B1 10 more at $.25 D1 last cost , which then would update showing

A1 previous balance 10 (or 30 if adding), Qty on hand 30, Last cost $.25 and E1 current avg $.58