The easiest fix is to create a database, with an entry form for data entry. Then when you need data back out, run a particular report. This will handle duplicates REALLY easy, and no code is needed!
Here is the problem with requests such as these: We spend some time writing up a solution based on the scope as described. Then the user, will post back, saying that it doesn't do the work right, and can we make more changes. We start tweaking on it, and then it still doesn't do what they need, because they forgot to mention a requirement in the beginning, and the whole thing needs to be re-engineered!
We do not provide turn key solutions for projects such as these, but we will assist when code needs to be Quality checked, or if the code is producing an error!
What error is your code producing?