Formula column and auto number concatenation


#1

I have a Sheet…
Work items … it is related to customers …

In the Work items sheet I have a field that has this formula in it …
Customer & “-” & AutoNumber

I want the auto number to be 1 more than the customers last work item for that customer and not the next auto number … is there an easy way to do this ?

Customer 1
Work item 1
Work item 2
Work item 3

Customer 2
Work item 4
Work item 7
Work item 8

Customer 3
Work item 5
Work item 6

What I want is this
Customer 1
Work item 1
Work item 2
Work item 3

Customer 2
Work item 1
Work item 2
Work item 3

Customer 3
Work item 1
Work item 2
Work item 3