I have a list of numerical items in column a, with corresponding info in
columns b-ab. I would like to a number to the item number at every change in
item. for example I would like to go from this:

10-1000
10-1000
10-1001
10-1001
10-1001
10-1003

to this:

10-1000 1
10-1000 1
10-1001 2
10-1001 2
10-1001 2
10-1003 3

the numbers are variable, as are the number of rows that they occupy.

Any thoughts much appreciated.

Breinn