JvCSVDataset: How to check if key already exists?

[webdev]

Hello. I am using Delphi 2010 to build a small application that builds a very very simple database in CSV file format. I am using the Jcl and JVCL libraries (TJvCSVDataset, TJvDataSource and TJvDBGrid). I set up the fields ("Last Name", "First Name" and "Email"), where "Email" is the only with...