Accounting for duplicates in a lookup

[tony tessman]

I have a table that has an order number, item number, date and serial number, I need to use a lookup to populate the serial number in another table. The problem is, an order number can have multiple of the same item number and each instance of items will have a unique serial number. I need a formula that will check if a serial number has been used (Populated into the table) and if so skip it and give the next serial number for the order number and item. Any ideas on how to do this would be much appreciated.

 

[kweaver]

Welcome.

It would be a big help if you illustrated part of your sheet and expected result(s) using XL2BB.