adding a number to every change in value

[Breinn]

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

 

[Bob Phillips]

B1: =A1&" " & 1
B2: =IF(A2=A1,B1,LEFT(B1,FIND(" ",B1))&RIGHT(B1,LEN(B1)-FIND(" ",B1)+1)+1)

 

[Breinn]

Perfect. You are my Excel hero.

B1: =A1&" " & 1
B2: =IF(A2=A1,B1,LEFT(B1,FIND(" ",B1))&RIGHT(B1,LEN(B1)-FIND(" ",B1)+1)+1)

 

[Bob Phillips]

I forgot to add ...

and copy down

But you knew that

Bob