Sorry I have already asked this but the answer has been lost somewhere, or i
can't find it now.

I have a list of data which i want to match the words then calculate the
difference between the first and second of the list, then sum all the
differences, i.e

bill 10
ben 9
fred 8
june 7
bill 6
ben 5
bill 4
ben 3
june 2

so i want it to return bill 6 (10-6 + 6-4), ben 6, june 5.

Any ideas on how to match the words, search for the next match then find the
differnce and keep that going for a list of 200 items with 20 different
names, summing all the differences?