averaging

[belvy123]

Hi All
I am working on a new sheet that I want to be able to keep a running average
of how long a certain part has been in use on our printing press

I want to be able to show the length of each individual part and the average
of three of these parts combined.
Also what I want to do is when I enter the date that a part has been changed
it will erase the oldest date of the three and move the others down and
update the average.
So what it will look like is this
( SEE BELOW)
Can anyone show me what type of formula or VB script I would need to be able
to do this

Thanks for the help
--



4/1/07 this set does not enterinto the average until it has
been changed
24 days out it is just showing how long it has been in service

3/30/07 used for average
27 days

3/24/07 used for average
33 days

3/20/07 used for average
37 days

Average =32.3 days




crunchnin numbers

 

[Cin]

There has to be a better way, but as there aren't any other responses yet:

=SUMIF(B1:B8,"used for average",A1:A8)/(COUNTIF(B1:B8,"used for average"))

Crude - but it works...