Validating date

I have the following situation. I have a pick list or bar codes that is provided as a CSV. I have written the macro to import this into a spreadsheet.
I now have to have an operator enter the bar code information and validate that the entry is part of the list.
There may be multiple entries for a given bar code, so when an entry matches, it needs to be removed from the original list leaving only the items remaining to be picked.
My difficulty is getting the validation of the information.
Any help would be greatly appreciated.
Thanks,