Maybe something like this:

With
A1:B10 containing your posted sample data

This formula returns the latest mileage increment
C6: =B6-LARGE(INDEX(($A$2:A6=A6)*$B$2:B6,0),2)
Copy that formula down

Is that something you can work with?
***********
Regards,
Ron

XL2002, WinXP


"Dave" wrote:

I have created a drivers system in excel, I require this system to
include mileages of the cars. I currently put the mileage reading into
a column and compare it to the last reading. I want the spreadsheet to
this automatically, which would save a great deal of time. So using
the example below the reading would get the new value for C which is
5890 and the of 5888 and deduce a figure of 2.

Hear is an example with the first four values being the start up
Mileages of the drivers.

Car Mileage Days Mileage
A 10145 -
B 8999 -
C 5888 -
D 7885 -
B 9019 20
D 7906 21
A 10190 45
D 7935 29
C 5890 2