Hope someoene can help with this. I have an excel sheet that I routinely import into Salesforce. The sheet is an extract from Sage containing data relating to Orders placed by Customers. Each row in the sheet contains an Order Number. If an order comprised five items then the order number would occur five times in the sheet.

What I want to do is apply a unique text string to each row comprising the Order Number and then a sequential number based on the number of occurrences in the list. E.g. if my list contained the following order numbers: 45678, 45699, 45678, 45234, 45672, 45699, 48230, 45678

I want a formula to create the following: 45678-1, 45699-1, 45678-2, 45234-1, 45672-1, 45699-2, 48230-1, 45678-3

I.e. 45678-3 is the third occurrence of the invoice number 45678 and so on.

Any ideas?

Thanks