I have a sheet that looks like
User# 1/10/2007 1/17/2007 1/21/2007
1 0 21 44
2 0 45 66
3 0 22 76
4 0 13 45
5 0 45 90

So basically, every week the number of columns will increase as I collect
more data -- my table continues getting bigger and bigger.
Someplace then I will have an column of equations for the current data
for each user that looks like
= (D2-c2) * something

Where "D2" and "C2" should be the two most recent columns in the above table


This seems like such an obvious thing, yet I've rarely seen a sample
spreadsheet that deals with a constantly growing table. I have struggled with
this problem in various forms for a long time and have never found a good
solution.
The alternative here would be to manually shift the data over each period
when
entering the new data - or manually edit those equations.