Hi. I would like help with the following problem. A1 contains the total job
costs and is constantly being updated. At the end of the first invoice
period I will type in the value from A1 into B1. Now on to my problem. For
following invoice periods I would like to subtract previous invoices from
the total job costs so that I only get the current invoice values.

A1 Total job costs being continuously updated
B1 At the end of two weeks I will type in the value from A1
C1 A1 minus B1
D1 A1 minus B1 and C1
E1 A1 minus B1 and C1 and D1
etc

Is there a formula that I can insert into cell C1 and just copy down. I
know that I could do this by typing in a unique formula into each cell, but I
am just hoping there is an easier way to do this. My spreadsheet actually
requires this process many times so any help you can send my way would be
extremely appreciated. I hope I have explained the problem clearly enough.

Gerd